GHSA-3vcm-c42p-3hhf — medium GitHub Advisory (CVE-2025-9076) in go/github.com/mattermost/mattermost…

Description

Mattermost versions 10.10.x <= 10.10.1 fail to properly sanitize user data during shared channel membership synchronization, which allows malicious or compromised remote clusters to access sensitive user information via unsanitized user objects. This vulnerability affects Mattermost Server instances with shared channels enabled.

Basic information

Type: reviewed
Severity: medium
Advisory on GitHub: Open advisory ↗
Repository advisory: —
Source code: Browse source ↗
Published (advisory): 2025-09-15 12:31:24 UTC
Updated: 2025-09-15 20:38:31 UTC
GitHub reviewed: 2025-09-15 20:38:31 UTC
NVD published: 2025-09-15

Score	Percentile
0.04%	13.83%

CVSS Scores

Base score	Version	Severity	Vector
6.5	3.1	—	`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:H) They need powerful rights—admin, root, or similar—before this pays off. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:N) Service keeps running; no real outage angle.

Identifiers

Type	Value
GHSA	GHSA-3vcm-c42p-3hhf ↗
CVE	CVE-2025-9076 ↗

CWEs

CWE id	Name
CWE-862	Missing Authorization

Affected packages (2)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem	Package	Vulnerable range	First patched	Vulnerable functions
go	github.com/mattermost/mattermost/server/v8	< 8.0.0-20250729073403-517ae758cd02	8.0.0-20250729073403-517ae758cd02	—
go	github.com/mattermost/mattermost-server	>= 10.10.0, < 10.10.2	10.10.2	—

Mattermost Missing Authorization vulnerability