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MEDIUM severity

Mattermost doesn't sanitize the Remote Cluster API response on PATCH operationsGHSA-9p44-r552-4wp9

MEDIUMFix: mattermost/mattermost#36313

GHSA-9p44-r552-4wp9 is a medium-severity (CVSS 6.5) CWE-201 vulnerability in github.com/mattermost/mattermost-server. A fix is available for github.com/mattermost/mattermost-server — see the affected versions and patch details below.

Also known asCVE-2026-7184GO-2026-6282
Published
Updated
Affected
4 pkgs
Patched
4 / 4
Exploits
None indexed
Exploitation data as of Oct 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-9p44-r552-4wp9.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk+0.18%
Lower risk than most CVEs36th percentile — riskier than 36% of all scored CVEsHighest risk
0.00%0.31%0.63%0.94%0.3%0.3%0.3%0.4%Jul 26Sep 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-9p44-r552-4wp9 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 384,534 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

4 pkgs affected
🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost/server/v8

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15 fail to sanitize the Remote Cluster API response on PATCH operations, which allows authenticated users with the {{manage_secure_connections}} permission to obtain remote cluster authentication tokens via a PATCH request to the remote cluster endpoint.. Mattermost Advisory ID: MMSA-2026-00662

Affected Packages

4 total 4 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/mattermost/mattermost-server≥ 11.6.0&&< 11.6.111.6.1go get github.com/mattermost/mattermost-server@v11.6.1
🐹Gogithub.com/mattermost/mattermost-server≥ 11.5.0&&< 11.5.511.5.5go get github.com/mattermost/mattermost-server@v11.5.5
🐹Gogithub.com/mattermost/mattermost-server≥ 10.11.0&&< 10.11.1610.11.16go get github.com/mattermost/mattermost-server@v10.11.16
🐹Gogithub.com/mattermost/mattermost/server/v8≥ 8.0.0-20250731163400-5b955468ea1e&&< 8.0.0-20260428142921-bd8fc92226728.0.0-20260428142921-bd8fc9222672go get github.com/mattermost/mattermost/server/v8@v8.0.0-20260428142921-bd8fc9222672

Affected Products

1 product · 3 configurations
Application
mattermost servermattermost
≥ 11.6.0 && < 11.6.2
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/mattermost/mattermost-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/mattermost/mattermost-server to 11.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9p44-r552-4wp9 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15 fail to sanitize the Remote Cluster API response on PATCH operations, which allows authenticated users with the {{manage_secure_connections}} permission to obtain remote cluster authentication tokens via a PATCH request to the remote cluster endpoint. Mattermost Advisory ID: MMSA-2026-00662
O3 Security · Impact-Aware SCA

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Mattermost doesn't sanitize the Remote Cluster API…