Zimbra Collaboration Suite PHP Remote File Inclusion Vulnerability

Historical catalog analysis: CISA added this entry on January 22, 2026. The entry reflects catalog information retrieved on August 31, 2026, not a snapshot archived on the inclusion date. Check current vendor guidance before acting.

What the vulnerability is

CVE-2025-68645 is a PHP remote file inclusion vulnerability (CWE-98) identified in the Synacor Zimbra Collaboration Suite (ZCS). The flaw exists at the /h/rest endpoint. According to reported details, a remote attacker could craft specific requests to this endpoint to influence internal request dispatching, which may enable the inclusion of arbitrary files located within the WebRoot directory.

Exposure and applicability

This vulnerability is applicable to healthcare providers, health plans, and business associates utilizing ZCS for email, scheduling, and administrative collaboration. Because these platforms often facilitate the transmission of electronic protected health information (ePHI) and critical clinical communications, an unauthorized file inclusion flaw could compromise the confidentiality of sensitive data stored on the server.

Organizations should determine if their current ZCS deployment exposes the /h/rest endpoint to untrusted networks and verify their specific version against vendor vulnerability disclosures.

Remediation priorities

Based on our analysis, healthcare IT and security leaders should prioritize the following actions to reduce risk:

1. Vendor Patching: The primary priority is to apply mitigations or updates as specified by Synacor. This addresses the root cause of the file inclusion flaw.
2. Endpoint Access Control: Review network access lists (ACLs) and firewall rules to restrict access to the /h/rest endpoint to only authorized internal IP addresses where possible, reducing the external attack surface.
3. Configuration Audit: Verify that the WebRoot directory contains only necessary files and that sensitive configuration files are stored outside of the web-accessible root to limit the impact of a potential file inclusion event.

How to validate remediation

To verify that exposure has been reduced, administrators should:
* Version Verification: Confirm that the installed ZCS version matches the patched version recommended by the vendor.
* Connectivity Testing: Use authorized network scanning tools to confirm whether the /h/rest endpoint is reachable from external, non-authorized networks.
* Log Review: Examine web server logs for unusual requests directed at the /h/rest path that may indicate attempted exploitation prior to patching.

Limits and open questions

While applying vendor mitigations reduces the likelihood of this specific vulnerability being exploited, it does not guarantee total immunity from other ZCS-related threats. It remains unknown whether this flaw has been utilized in active ransomware campaigns. Furthermore, while CISA has established a remediation deadline for federal agencies, this date serves as a risk benchmark rather than a legal requirement for private healthcare entities under HIPAA.

Source and editorial note

CVE-2025-68645: Synacor Zimbra Collaboration Suite (ZCS) PHP Remote File Inclusion Vulnerability · Source date: January 22, 2026 · Retrieved August 31, 2026.

Material facts are tied to the cited primary source. Recommendations are independent defensive analysis unless attributed to the source. Confirm consequential decisions against current authoritative guidance.

Archive date: January 25, 2026. The displayed post date is assigned three days after the source date to organize this retrospective archive; it does not mean this site published the analysis then. First published by this site: September 21, 2026 at 01:06 UTC.

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