Zimbra Collaboration Suite OnlyOffice Integration Path Traversal Leading to Remote Code Execution via Unauthenticated /downloadas Request

published 2026-09-25 44 d ago modified 2026-09-29 40 d ago also EUVD-2026-87101

cvss: 9.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.0%; EPSS 1.0% chance of exploitation in 30 days, percentile 61%
public exploits: 0; none known

When OnlyOffice/Document Editing is available, an unauthenticated remote attacker with access to an existing supported public Briefcase document can abuse unsigned save fields to perform path-traversal writes and execute commands as zimbra.

Patch / fix

fixed in 1

Zimbra Zimbra Collaboration Suite (ZCS) 10.1.21

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: 45 d ago (2026-09-25)

Exploit prediction

0.96% chance of exploitation in the next 30 days, higher than 61% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Zimbra Zimbra Collaboration Suite (ZCS)

Classification

Weakness

CWE-22 Improper Limitation of a Pathname to a Restricted Directory
CWE-863 Incorrect Authorization

References

wiki.zimbra.com /wiki/Zimbra_Security_Advisories
vendor-advisory

Sources

CVE List CVE-2026-93643
NVD CVE-2026-93643

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary