CVE-2026-93633 json
Zimbra Collaboration Suite Briefcase CSS Sanitization Bypass via Non-ASCII Stylesheet Characters
published 2026-10-23 17 d ago modified 2026-10-28 11 d ago also EUVD-2026-108973
- cvss
- 5.4
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 14%
- public exploits
- 0
- none known
Summary
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.
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 11 d ago
Exploit prediction
0.23% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- rapid7.com https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N |
Affected products
- Zimbra Zimbra Collaboration Suite
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
References
-
rapid7.com
/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/
related, exploit, third-party-advisory
-
wiki.zimbra.com
/wiki/Zimbra_Security_Advisories
vendor-advisory
Sources
- CVE List CVE-2026-93633
- NVD CVE-2026-93633
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