CVE-2025-13767: Unauthorized Read Access to Private Channel Posts via Mattermost Jira Plugin

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-24 · updated 2026-10-19
Weakness: CWE-863

Description

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 fails to validate user channel membership when attaching Mattermost posts as comments to Jira issues, which allows an authenticated attacker with access to the Jira plugin to read post content and attachments from channels they do not have access to.

Affected products

Mattermost: from 10.11.0 before 10.11.8; from 10.12.0 before 10.12.4; from 11.0.0 before 11.0.6; from 11.1.0 before 11.1.1 — fixed in 10.11.8, 10.12.4, 11.0.6, 11.1.1

How to fix

Upgrade to a fixed version: Mattermost 10.11.8, 10.12.4, 11.0.6, 11.1.1. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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