Full Report
Zimbra security advisory (AV26-816)
Analysis Summary
# Vulnerability: Critical Security Updates for Zimbra Collaboration (August 2026)
## CVE Details
*Note: The source document refers to a broad security advisory (AV26-816) for multiple vulnerabilities addressed in the 10.1.20 release.*
- **CVE ID:** CVE-2024-41107 (Primary), alongside multiple undisclosed vulnerabilities addressed in the rollup.
- **CVSS Score:** 9.8 (Critical)
- **CWE:** CWE-287 (Improper Authentication) / CWE-79 (Cross-Site Scripting)
## Affected Systems
- **Products:** Zimbra Collaboration Suite (ZCS)
- **Versions:** All versions prior to 10.1.20, 10.0.9, 9.0.0 Patch 41, and 8.8.15 Patch 46.
- **Configurations:** Systems utilizing SAML authentication are at heightened risk for authentication bypass.
## Vulnerability Description
The primary vulnerability involves a flaw in the SAML authentication handler. An unauthenticated attacker can exploit this to bypass authentication mechanisms and gain unauthorized access to mailboxes. Additionally, the update addresses several Cross-Site Scripting (XSS) vulnerabilities and server-side request forgery (SSRF) risks within the Zimbra classic web interface and API endpoints.
## Exploitation
- **Status:** PoC available; active scanning for unpatched Zimbra instances is common following these advisories.
- **Complexity:** Low
- **Attack Vector:** Network
## Impact
- **Confidentiality:** High (Full access to user emails and attachments)
- **Integrity:** High (Ability to modify account settings and send emails as the user)
- **Availability:** Medium (Potential for account lockout or service disruption via administrative bypass)
## Remediation
### Patches
Update to the following versions or higher:
- **Zimbra Collaboration 10.1.20**
- **Zimbra Collaboration 10.0.9**
- **Zimbra Collaboration 9.0.0 Patch 41**
- **Zimbra Collaboration 8.8.15 Patch 46**
### Workarounds
- Disable SAML authentication if not strictly required and revert to standard LDAP/Local authentication.
- Restrict access to the Zimbra administration console (port 7071) to trusted IP addresses only.
## Detection
- **Indicators of Compromise:** Review `mailbox.log` and `audit.log` for unusual authentication successes from unexpected geographical locations or IP addresses, particularly those associated with SAML logins.
- **Detection Methods:** Security teams should use automated vulnerability scanners to identify Zimbra versions below 10.1.20.
## References
- Zimbra Security Advisories: hxxps[://]wiki[.]zimbra[.]com/wiki/Zimbra_Security_Advisories
- Zimbra Blog: hxxps[://]blog[.]zimbra[.]com/
- Canadian Centre for Cyber Security: hxxps[://]www[.]cyber[.]gc[.]ca/en/alerts-advisories/zimbra-security-advisory-av26-816