CVE-2026-93647: Zimbra Collaboration Suite (ZCS) · Cross-site Scripting
Affects Zimbra Collaboration Suite (ZCS)Source CVE Database V5
Not known to be exploited · CVSS 9.3 Critical : upgrade to 10.1.21 as a priority.
Data as of 8 Nov 2026, 23:24 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 13% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 10.1.21
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 25 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 8 Nov 2026.
What to do
Upgrade Zimbra Collaboration Suite (ZCS) to 10.1.21.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| ZimbraZimbra Collaboration Suite (ZCS) | Affected
| Fixed in
|
AI-suggested
If you cannot patch yet, users should exercise caution when interacting with calendar messages from untrusted sources. Consider disabling or restricting calendar message rendering in Zimbra Classic if possible.
Description
An unauthenticated calendar sender can place active markup in a COUNTER message's RFC From address. Selecting the message in Zimbra Classic triggers stored XSS, allowing the attacker to access mailbox data and act as the victim.