Guest user can discover archived public channels

published 2025-11-14 11 mo ago modified 2026-10-19 21 d ago also GHSA-j6gg-r5jc-47cm , GO-2025-4126 , EUVD-2025-186558

cvss: 4.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 10%
public exploits: 0; none known

Mattermost versions <11 fail to properly restrict access to archived channel search API which allows guest users to discover archived public channels via the `/api/v4/teams/{team_id}/channels/search_archived` endpoint

Patch / fix

fixed in 6 distros 1 links 1

go github.com/mattermost/mattermost/server/v8 8.0.0-20250815165020-c8d66301415d
go github.com/mattermost/mattermost 5.3.2-0.20250815165020-c8d66301415d
go github.com/mattermost/mattermost-server 5.3.2-0.20250815165020-c8d66301415d
go github.com/mattermost/mattermost-server/v5 5.3.2-0.20250815165020-c8d66301415d
go github.com/mattermost/mattermost-server/v6 5.3.2-0.20250815165020-c8d66301415d
Mattermost Mattermost 11.0.0

govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

github.com/mattermost/mattermost@c8d6630 commit

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 11 mo ago (2025-11-14)

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 10% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
GitHub	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
go	github.com/mattermost/mattermost/server/v8	<8.0.0-20250815165020-c8d66301415d	8.0.0-20250815165020-c8d66301415d
go	github.com/mattermost/mattermost	<5.3.2-0.20250815165020-c8d66301415d all versions	5.3.2-0.20250815165020-c8d66301415d
go	github.com/mattermost/mattermost-server	<5.3.2-0.20250815165020-c8d66301415d all versions	5.3.2-0.20250815165020-c8d66301415d
go	github.com/mattermost/mattermost-server/v5	<5.3.2-0.20250815165020-c8d66301415d all versions	5.3.2-0.20250815165020-c8d66301415d
go	github.com/mattermost/mattermost-server/v6	<5.3.2-0.20250815165020-c8d66301415d all versions	5.3.2-0.20250815165020-c8d66301415d
go	github.com/mattermost/mattermost/v5	all versions	no fix listed

Affected products

Mattermost Mattermost

Classification

Weakness

CWE-863 Incorrect Authorization

References

github.com /mattermost/mattermost/commit/c8d66301415d5b447df0e829bdbaa92e8a83ecf8
web, patch
mattermost.com /security-updates
web, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2025-11776
advisory
github.com /advisories/GHSA-j6gg-r5jc-47cm
advisory

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary