What’s Vulnerable › Vulnerabilities

CVE-2026-10106: Unauthorized users can trigger interactive post actions in private channels via action cookie channel mismatch in Mattermost

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-13 · updated 2026-07-13
• Weakness: CWE-863

Description

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to verify that the channel referenced in an action cookie matches the channel of the target post, which allows an authenticated user without access to a private channel to trigger interactive post actions on posts in that channel via a cookie obtained from any accessible channel.. Mattermost Advisory ID: MMSA-2026-00690

Affected products

• Mattermost: from 10.11.0 before 10.11.20; from 11.6.0 before 11.6.5; from 11.7.0 before 11.7.3 — fixed in 10.11.20, 11.6.5, 11.7.3

How to fix

Upgrade to a fixed version: Mattermost 10.11.20, 11.6.5, 11.7.3. Check the vendor advisory for mitigations.

References

• https://mattermost.com/security-updates

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