Synacor Zimbra Collaborate Suite (ZCS) Cross-Site Scripting Vulnerability
Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting (XSS) vulnerability in the Calendar feature that allows an attacker to execute arbitrary code.
A remote attacker, without authentication, can achieve partial data exposure, partial data tampering. CISA has confirmed use of this vulnerability in known ransomware campaigns — treat as high priority for remediation. Federal agencies are required to remediate by 2022-03-11 under CISA BOD 22-01.
This is a Software Vulnerability (CWE-116) (CWE-116) vulnerability in Synacor Zimbra Collaborate Suite (ZCS). An issue was discovered in the Calendar feature in Zimbra Collaboration Suite 8.8.x before 8.8.15 patch 30 (update 1), as exploited in the wild starting in December 2021. An attacker could place HTML containing executable JavaScript inside element attributes. This markup becomes unescaped, causing arbitrary markup to be injected into the document. 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:
Used in known ransomware campaigns. Threat-research write-up: https://www.volexity.com/blog/2022/02/03/operation-emailthief-active-exploitation-of-zero-day-xss-vulnerability-in-zimbra/
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 updates per vendor instructions.
References
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References