CVE-2026-100404GHSA-5r8f-gq2h-fcgp
Zulip: Guests can read new messages in non-subscribed public channels
zulip zulip
CVSS
6.5MediumExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.41%Chance of exploitation activity in the next 30 days, higher than 34% of CVEs. Scored 23 Oct 2026FIRST EPSS
What fixes it
- 12.2Zulip serverGitHub
A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.
Description
Zulip is an open-source team collaboration tool. In Zulip Server versions through 12.1, guest users can receive new message events for public channels outside their subscriptions. A guest can trigger the issue by registering an event queue with parameters that request messages from an unsubscribed public channel, or an existing event queue can remain affected after the guest's access to the channel is removed. The flaw discloses new public-channel messages to the guest. This issue is fixed in version 12.2.
Text from CVE List
Affected versions 2
- zulipaffected: < 12.2CVE List
- Zulip server<= 12.1GitHub
References 5
- github.com/zulip/zulip/commit/98659a41cb93d4ce329ea14bb0cdfb4b147500baFixvia CVE List
- github.com/zulip/zulip/commit/c03db8916456674df3c98614f6f0ef8cd024ef11Fixvia CVE List
- github.com/zulip/zulip/releases/tag/12.2Fixvia CVE List
- github.com/zulip/zulip/security/advisories/GHSA-5r8f-gq2h-fcgpAdvisoryvia CVE List
- github.com/zulip/zulip/pull/39913Referencevia CVE List