MSRXCVE-2026-93633
CVE-2026-93633
Zimbra Collaboration Suite Briefcase CSS Sanitization Bypass via Non-ASCII Stylesheet Characters
CVSS 3.1 · CNA · rapid7.com
chance of exploitation in the next 30 days (EPSS; higher than 14% of CVEs)
A CSS sanitization vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user with Briefcase access to publish a document that displays attacker-controlled content under the Zimbra origin. When processing a stylesheet containing non-ASCII characters, DefangFilter appends the final ASCII segment without sanitizing it. HTML stored as application/x-zimbra-doc can therefore retain CSS URL references that the normal sanitizer removes. An attacker can share a crafted document that loads external resources and displays a credential-collection form using Zimbra's own visual assets. Exploitation requires the victim to open the document in a browser that renders the content type inline; credential theft additionally requires form submission. ZCS 10.1.16 and 10.1.20 are affected.
Scores
Affected products
- synacor zimbra collaboration suite: ≤ 10.1.20
Weakness: CWE-79
2 references (advisories, patches, write-ups)
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories · Vendor Advisory
- https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ · Exploit, Third Party Advisory
Sources: NVD, CVE.org, FIRST EPSS. Missing ones did not answer or have no record yet.