CVE Identifier: CVE-2025-68645
Disclosure Date: December 22–23, 2025
Severity: High to Critical (depending on scoring system)
Affected Software: Zimbra Collaboration Suite (ZCS) Webmail Classic UI versions 10.0 and 10.1
Vulnerability Class: Local File Inclusion (LFI) / Improper Input Handling
Overview
CVE-2025-68645 is a high-severity Local File Inclusion vulnerability affecting the Webmail Classic UI of Zimbra Collaboration Suite versions 10.0 and 10.1. The flaw arises from improper handling of user-supplied input within the Classic UI’s REST processing logic. Due to insufficient validation, an attacker can manipulate request parameters in a way that causes the application to include unintended local files from the server’s web root.
What makes this vulnerability particularly serious is that exploitation can be performed remotely and does not require authentication, significantly increasing the exposure for internet-facing Zimbra deployments.
Technical Summary
The vulnerability exists in the Classic Webmail REST interface, where user-controlled parameters are passed to a servlet responsible for handling REST requests. Because these parameters are not properly sanitized or constrained, an attacker can craft a malicious HTTP request that forces the application to reference files that should not be accessible through the web interface.
This type of weakness is commonly categorized as a Local File Inclusion issue, where the application’s file handling logic can be abused to read internal files that reside on the same system.
Severity and Impact
Under modern CVSS v3.1 scoring, CVE-2025-68645 is rated as High severity, reflecting the following risk factors:
- Network-based attack vector
- Low attack complexity
- No privileges required
- Potentially high impact on confidentiality, integrity, and availability
Some legacy scoring systems rate the issue as Critical, emphasizing the worst-case impact if sensitive files are disclosed or if the vulnerability is chained with other flaws.
If successfully exploited, this vulnerability could allow an attacker to:
- Read sensitive configuration files
- Access internal application resources
- Gain information that could be used for further compromise, such as credential harvesting or follow-on attacks
Because the Classic UI is still widely deployed, the overall risk to organizations running affected versions is substantial.
Exploitation Risk
Although no public exploit details are required for the vulnerability to be dangerous, Local File Inclusion issues are well understood and frequently targeted by attackers. Any Zimbra server exposing the Classic Webmail interface to untrusted networks is at increased risk, particularly if patching is delayed.
Even limited file disclosure can be enough to undermine the security of the entire mail platform when combined with other weaknesses.
Mitigation and Defensive Measures
Organizations running affected Zimbra versions should take immediate steps to reduce exposure:
- Apply vendor patches as soon as updated releases addressing CVE-2025-68645 become available.
- Restrict external access to the Webmail Classic UI where possible, especially for administrative or legacy interfaces.
- Monitor HTTP request logs for unusual access patterns targeting REST endpoints.
- Use perimeter defenses such as firewalls or web application firewalls to detect and block suspicious request patterns associated with file inclusion attacks.
Longer term, organizations should consider minimizing reliance on legacy web interfaces and ensuring that all externally accessible services are routinely reviewed for input validation weaknesses.
Conclusion
CVE-2025-68645 highlights the ongoing risk posed by input validation flaws in complex web applications. As a remotely exploitable, unauthenticated Local File Inclusion vulnerability, it represents a serious threat to affected Zimbra Collaboration Suite deployments. Prompt patching, access control, and monitoring are essential to prevent potential data exposure and downstream compromise.
