Cve20207796 Zimbra Collaboration Suite Fix Full 〈PLUS × RELEASE〉
Maya, a senior security analyst. She’s reviewing a routine vulnerability scan report from the previous night.
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 (due to misconfigured or default proxy routes), the attacker can force any logged-in Zimbra user to execute arbitrary JavaScript in their browser context.
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.
Attackers do not need to log in to the server.
Here:
: After upgrading, administrators should use the zmcontrol -v command to verify the current patch level. 2. Immediate Temporary Mitigations
CVE-2020-27996 is a classic but powerful reflected XSS flaw in Zimbra Collaboration Suite, made severe due to Zimbra’s complex routing and proxy architecture. While its CVSS score is “Medium,” its real-world impact — especially when combined with CVE-2020-27995 — is . Administrators must patch immediately or apply strict URL filtering to prevent exploitation.
At its core, the vulnerability is a classic case of insufficient input validation. The Zimbra server blindly trusted a URL provided by a remote, unauthenticated attacker and initiated a request to that location. The server executed this request with its own privileges, effectively acting as an unwitting proxy.
To secure your Zimbra Collaboration Suite installation, consider the following: cve20207796 zimbra collaboration suite full
An unauthenticated attacker sends a tailored HTTP POST or GET request containing a target URL pointing to an internal resource (e.g., http://127.0.0 or cloud metadata endpoints like http://169.254.169 ). The Zimbra server implicitly trusts its internal framework, executes the request on behalf of the attacker, and forwards the response back to the malicious source. Potential Impact on the Enterprise
As of today, Zimbra has fixed this issue, but scanning data shows that as of late 2022, over 8,000 Zimbra servers remained vulnerable to CVE-2020-27996. If you are running an older Zimbra instance, stop reading—and start patching.
Malicious requests can extract highly sensitive infrastructure information, local configuration files, or administrative credentials stored within internal endpoints.
Once RCE is achieved:
# For Ubuntu/Debian based operating systems apt-get update && apt-get install zimbra-core zimbra-store # For RHEL/CentOS based operating systems yum clean all && yum update zimbra-core zimbra-store Use code with caution.
Last updated: 2026-04-19 References: NVD, Zimbra Security Advisories, Rapid7 Analysis, Project Discovery research.
CVE-2020-7796 is a significant vulnerability in the Zimbra Collaboration Suite that can lead to unauthorized access to sensitive information. Organizations using the platform should take immediate action to mitigate the effects of this vulnerability by updating to a patched version, implementing additional security measures, and monitoring for suspicious activity. By taking these steps, organizations can protect their sensitive data and prevent exploitation.
Administrators must secure their environments immediately, as massive scanning and exploitation attempts have been actively logged. 1. Upgrade Zimbra Maya, a senior security analyst
: Synacor Zimbra Collaboration Suite (ZCS) versions before 8.8.15 Patch 7 .
nuclei -t cves/2020/CVE-2020-7796.yaml -u https://yourcompany.com Use code with caution. 2. Log Analysis