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Known exploited vulnerability · CISA KEV

CVE-2022-27926: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability

Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability by allowing an endpoint URL to accept parameters without sanitizing.

CVE-2022-27926

Exploited in the wild. Fix this first.

CISA added it to the Known Exploited Vulnerabilities catalog on 2023-04-03: attackers are using it right now.

CISA KEV
Listed
Added 2023-04-03 · federal fix-by 2023-04-24
EPSS (30 days)
18%
Higher than 97% of CVEs · 2026-11-01
CVSS v3.1
6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

What CISA says

Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability

Apply updates per vendor instructions.

NVD description · published 2022-04-21

A reflected cross-site scripting (XSS) vulnerability in the /public/launchNewWindow.jsp component of Zimbra Collaboration (aka ZCS) 9.0 allows unauthenticated attackers to execute arbitrary web script or HTML via request parameters.

Full record on NVD

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How to check if you are exposed to CVE-2022-27926

  1. Find every Synacor Zimbra Collaboration Suite (ZCS) system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
  2. Compare each version with the fixed versions in the vendor advisory below. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
  3. Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2022-27926.

US federal agencies had to fix this by 2023-04-24. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.

Affected versions

Versions the National Vulnerability Database lists as vulnerable to CVE-2022-27926. Check the vendor advisory for the exact fixed builds before you sign anything off.

ProductVulnerable versions
Synacor Zimbra Collaboration Suite9.0.0; 9.0.0-p1; 9.0.0-p10; 9.0.0-p11; 9.0.0-p12; 9.0.0-p13 and 18 more

Timeline

  1. · Published in the National Vulnerability Database
  2. · Added to CISA's Known Exploited Vulnerabilities catalog, 347 days after it was published
  3. · Fix-by date for US federal agencies, passed 1,287 days ago

Vendor advisories and fixes

Weakness type

More exploited Synacor vulnerabilities

CISA lists 19 exploited Synacor vulnerabilities. The closest matches:

Keep going

Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

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