CVE-2025-68645: Zimbra Collaboration Path Traversal Flaw

CVE-2025-68645 Overview

A Local File Inclusion (LFI) vulnerability exists in the Webmail Classic UI of Zimbra Collaboration Suite (ZCS) versions 10.0 and 10.1 due to improper handling of user-supplied request parameters in the RestFilter servlet. An unauthenticated remote attacker can craft malicious requests to the /h/rest endpoint to influence internal request dispatching, allowing inclusion of arbitrary files from the WebRoot directory. This vulnerability poses significant risks to organizations using Zimbra for email and collaboration services.

Critical Impact

This actively exploited vulnerability allows unauthenticated attackers to include arbitrary files from the WebRoot directory, potentially exposing sensitive configuration data, credentials, or enabling further exploitation chains. CISA has added this vulnerability to their Known Exploited Vulnerabilities catalog.

Affected Products

• Synacor Zimbra Collaboration Suite 10.0
• Synacor Zimbra Collaboration Suite 10.1
• Zimbra Collaboration Webmail Classic UI

Discovery Timeline

• 2025-12-22 - CVE-2025-68645 published to NVD
• 2026-01-23 - Last updated in NVD database

Technical Details for CVE-2025-68645

Vulnerability Analysis

This Local File Inclusion vulnerability (CWE-98) stems from insufficient input validation in the Zimbra Collaboration Suite's RestFilter servlet. The vulnerability allows attackers to manipulate request parameters sent to the /h/rest endpoint, which handles REST API calls in the Classic Webmail interface. By crafting specially designed HTTP requests, attackers can bypass security controls and influence how internal requests are dispatched and processed.

The vulnerability is particularly dangerous because it requires no authentication to exploit. Attackers can remotely target exposed Zimbra servers over the network, though user interaction is required for successful exploitation. The impact encompasses confidentiality, integrity, and availability concerns—successful exploitation can lead to unauthorized access to sensitive files, potential system compromise, and service disruption.

Root Cause

The root cause of CVE-2025-68645 lies in the improper handling and validation of user-supplied request parameters within the RestFilter servlet component. The servlet fails to adequately sanitize input before processing file inclusion requests, allowing path manipulation that can reference files outside the intended scope. This insufficient input validation enables attackers to influence internal request dispatching mechanisms and include arbitrary files from the WebRoot directory structure.

Attack Vector

The attack vector for this vulnerability is network-based, targeting the /h/rest endpoint accessible through the Zimbra Webmail Classic UI. An attacker can craft malicious HTTP requests containing specially formed parameters that exploit the improper input handling in the RestFilter servlet. When these requests are processed, the server includes files from unintended locations within the WebRoot directory.

The exploitation flow typically involves:

1. Identifying a vulnerable Zimbra server with the Classic UI enabled
2. Crafting HTTP requests with manipulated parameters targeting the /h/rest endpoint
3. Exploiting the RestFilter servlet's improper parameter handling to influence request dispatching
4. Including arbitrary files from the WebRoot directory in the server's response

For detailed technical information about the vulnerability mechanism and exploitation techniques, refer to the Zimbra Security Center advisory.

Detection Methods for CVE-2025-68645

Indicators of Compromise

• Unusual HTTP requests to the /h/rest endpoint containing path traversal sequences or unexpected parameters
• Abnormal access patterns to the Zimbra Webmail Classic UI from external IP addresses
• Log entries showing attempts to access files outside normal application paths within WebRoot
• Unexpected file access or read operations in Zimbra server logs

Detection Strategies

• Monitor and alert on HTTP requests to /h/rest endpoints that contain suspicious parameter values or path manipulation attempts
• Implement Web Application Firewall (WAF) rules to detect and block Local File Inclusion patterns targeting Zimbra servers
• Deploy endpoint detection solutions like SentinelOne to identify post-exploitation activities and anomalous file access patterns
• Review Zimbra access logs for requests from unfamiliar IP addresses or unusual geographic locations

Monitoring Recommendations

• Enable verbose logging on Zimbra servers to capture detailed request information for forensic analysis
• Configure real-time alerting for any requests matching LFI attack signatures targeting the Classic UI
• Implement network traffic analysis to detect exploitation attempts at the network perimeter
• Regularly review server logs for patterns consistent with reconnaissance or exploitation activity

How to Mitigate CVE-2025-68645

Immediate Actions Required

• Apply the latest security patches from Zimbra immediately as this vulnerability is actively exploited in the wild
• If patching is not immediately possible, consider temporarily disabling the Classic Webmail UI and using only the modern interface
• Review server logs for any evidence of exploitation attempts or successful compromise
• Implement network-level access controls to restrict access to Zimbra servers from trusted networks only

Patch Information

Synacor has released security updates to address CVE-2025-68645. Organizations should consult the Zimbra Security Center for the latest patch information and update instructions. Given that this vulnerability has been added to CISA's Known Exploited Vulnerabilities catalog, federal agencies and critical infrastructure organizations should prioritize remediation according to CISA guidance.

Workarounds

• Disable the Classic Webmail UI if not required and enforce use of the modern web interface
• Implement strict Web Application Firewall rules to filter requests containing path traversal or LFI attack patterns
• Restrict network access to Zimbra servers using firewall rules, limiting exposure to trusted IP ranges
• Enable additional logging and monitoring on the /h/rest endpoint to detect exploitation attempts

# Example: Restrict access to Zimbra web services at the firewall level
# Allow only trusted networks to access Zimbra webmail
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP

# Monitor Zimbra access logs for suspicious activity
tail -f /opt/zimbra/log/access_log* | grep -E '/h/rest.*\.\.'