CVE-2026-100404
Zulip: Guests can read new messages in non-subscribed public channels
- State
- Published
- Severity
- 6.5 Medium
- Published
- Oct 14, 2026
- Updated
- Oct 29, 2026
- Reserved
- Sep 25, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 6.5 Medium | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N | GitHub_M |
Weaknesses
- CWE-862 Missing Authorization
Affected Products
| Product | Versions |
|---|---|
zulipzulip |
|
References
- https://github.com/zulip/zulip/security/advisories/GHSA-5r8f-gq2h-fcgp
- https://github.com/zulip/zulip/pull/39913
- https://github.com/zulip/zulip/commit/98659a41cb93d4ce329ea14bb0cdfb4b147500ba
- https://github.com/zulip/zulip/commit/c03db8916456674df3c98614f6f0ef8cd024ef11
- https://github.com/zulip/zulip/releases/tag/12.2
Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.