Cve20207796 - Zimbra Collaboration Suite Full

Look for the following in Zimbra logs (/opt/zimbra/log/access_log.nginx*, mailbox.log):

GET /service/home/~/?auth=co&fmt=riched&user=INBOX%22%3E%3Cscript%3E
POST /service/proxy?target=https://attacker.com/
Abnormal Calendar invite with HTML payload in DESCRIPTION field

Also monitor for:

CVE-2020-7796 serves as a stark reminder of the risks associated with complex enterprise collaboration suites. The combination of an unrestricted upload feature and improper access controls created a "full" compromise scenario for thousands of mail servers. For organizations using Zimbra, continuous patching and rigorous monitoring of web directories remain the most effective defenses against such vulnerabilities.

Understanding CVE-2020-7796: The SSRF Threat to Zimbra Collaboration Suite

Zimbra Collaboration Suite (ZCS) is a widely used enterprise-level email and collaboration platform. However, versions prior to 8.8.15 Patch 7 are vulnerable to a significant security flaw identified as CVE-2020-7796 What is CVE-2020-7796? CVE-2020-7796 is a Server-Side Request Forgery (SSRF)

vulnerability. It occurs due to insufficient validation of user-supplied URLs within specific components of the Zimbra application. Specifically, this vulnerability is triggered when the WebEx zimlet is installed and the zimlet JSP is enabled. How the Vulnerability Works

In an SSRF attack, an unauthenticated remote attacker can force the vulnerable Zimbra server to make HTTP requests to arbitrary internal or external hosts. Internal Proxying

: Attackers can use the server as a proxy to reach internal services that are not normally accessible from the public internet. Data Exposure

: This can lead to unauthorized access to sensitive internal data or administrative interfaces. Arbitrary Requests

: The server essentially becomes a tool for the attacker to send requests to other systems under the guise of the trusted Zimbra server. Impact and Risk

: High. Because it can be exploited by unauthenticated attackers, it poses a direct risk to any exposed Zimbra instance. Potential Outcomes

: Data leakage, internal network scanning, and potential escalation if internal services have weaker authentication than public ones. Remediation: How to Protect Your Server

The primary way to mitigate this risk is to update your Zimbra installation to a secure version. Upgrade ZCS : Apply the latest patches or upgrade to Zimbra Collaboration Suite version 8.8.15 Patch 7 or higher. Verify Patching : You can check for updates and install the latest zimbra-patch package using system tools like Monitor Zimlets cve20207796 zimbra collaboration suite full

: If you cannot patch immediately, consider disabling the WebEx zimlet or zimlet JSP functionality if they are not critical to your operations. For more details on official patches, refer to the Zimbra Wiki Security Center for Zimbra 8.8.15? 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 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:

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: 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:

Solution

To mitigate this vulnerability, administrators are advised to:

Proof-of-Concept

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

Recommendations

References

Please let me know if you'd like me to modify anything! Look for the following in Zimbra logs (

Update Here are some suggestions to harden and Secure Zimbra

Secure Zimbra Collaboration Suite

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

Additional Security Measures

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

Resources

If you suspect a Zimbra server was exploited pre-patch, look for the following IoCs (Indicators of Compromise):

Once RCE is achieved:

Zimbra released patches addressing this vulnerability. Organizations must upgrade to the latest patched versions immediately:

Note: The patch updates the unrar binary to a version that addresses the buffer overflow.