Vulnerability in Zimbra Collaboration Suite

[ Description ]Official description

An authentication rate-limit bypass in Zimbra Collaboration Suite 10.1.0 through 10.1.21 allows unauthenticated attackers to make repeated password guesses through GraphQL without incrementing Zimbra’s source-IP failure counter. GraphQL aliases allow multiple authentication attempts in one HTTP request.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund14 Oct 2026WID-SEC-2026-3977

  Synacor Zimbra: Multiple vulnerabilities Translated from German

  CVE-2026-93635CVE-2026-93637

[ References ]References

• www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1