Synacor Zimbra Collaboration Suite (ZCS) PHP Remote File Inclusion Vulnerability
Synacor Zimbra Collaboration Suite (ZCS) contains a PHP remote file inclusion vulnerability that could allow for remote attackers to craft requests to the /h/rest endpoint to influence internal request dispatching, allowing inclusion of arbitrary files from the WebRoot directory.
A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2026-02-12 under CISA BOD 22-01.
This is a Software Vulnerability (CWE-98) (CWE-98) vulnerability in Synacor Zimbra Collaboration Suite (ZCS). A Local File Inclusion (LFI) vulnerability exists in the Webmail Classic UI of Zimbra Collaboration (ZCS) 10.0 and 10.1 because of improper handling of user-supplied request parameters in the RestFilter servlet. An unauthenticated remote attacker can craft requests to the /h/rest endpoint to influence internal request dispatching, allowing inclusion of arbitrary files from the WebRoot directory. Exploitation requires remote network access, low attack complexity, no authentication required, and user interaction required.
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Phishing link
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Malicious file
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Server compromised
Probably yes if any of these apply:
CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2026-01-22 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2026-02-12.
Manual remediation steps
Apply the Vendor Patch
This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.
CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
References
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References