CVE-2026-100404

Zulip: Guests can read new messages in non-subscribed public channels

Published Oct 14, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Zulip
Zulip zulip
Vendors & Products Zulip
Zulip zulip
Type Values Removed Values Added
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.
Title Zulip: Guests can read new messages in non-subscribed public channels
Weaknesses CWE-862
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 29, 2026, 2:20 PM
Reserved
Sep 25, 2026, 8:08 PM
Status
Awaiting Analysis
Published
Oct 14, 2026, 4:17 PM
Modified
Oct 29, 2026, 3:17 PM