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MEDIUM severity

CVE-2025-12756 — server

MEDIUM

CVE-2025-12756 is a medium-severity (CVSS 4.3) CWE-863 vulnerability in github.com/mattermost/mattermost/server/v8. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Insecure Direct Object Reference in Mattermost Boards Plugin Enables Unauthorised Comment Deletion

Also known asGHSA-p6gj-jc38-x2m7GO-2025-4172
Published
Updated
Affected
5 pkgs
Patched
See advisory
Exploits
None indexed
Exploitation data as of Nov 5, 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 CVE-2025-12756.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs9th percentile — riskier than 9% of all scored CVEsHighest risk
0.00%0.23%0.46%0.70%0.0%0.2%May 26Sep 26Nov 26

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

5 pkgs affected
🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost🐹github.com/mattermost/mattermost🐹github.com/mattermost/mattermost🐹github.com/mattermost/mattermost

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 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to validate user permissions when deleting comments in Boards, which allows an authenticated user with the editor role to delete comments created by other users.

Affected Packages

5 total
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/mattermost/mattermost/server/v8all versionsNo fix
🐹Gogithub.com/mattermost/mattermost≥ 10.11.0No fix
🐹Gogithub.com/mattermost/mattermost≥ 10.12.0No fix
🐹Gogithub.com/mattermost/mattermost≥ 10.5.0No fix
🐹Gogithub.com/mattermost/mattermost≥ 11.0.0No fix

Affected Products

1 product · 4 configurations
Application
mattermost servermattermost
≥ 11.0.0 && < 11.0.3
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/v8, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    The records we use list no patched version of github.com/mattermost/mattermost/server/v8 for CVE-2025-12756. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to validate user permissions when deleting comments in Boards, which allows an authenticated user with the editor role to delete comments created by other users.
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CVE-2025-12756: server (Medium 4.3)