What’s Vulnerable › Vulnerabilities
CVE-2026-19541: Outgoing OAuth connection client secret exposure during connection validation
- Severity: medium (CVSS 6.5 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: 2026-10-16 · updated 2026-10-29
- Weakness: CWE-201
Description
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to require re-entry of the stored client secret when validating an outgoing OAuth connection, which allows an authenticated user with permission to manage outgoing OAuth connections to obtain the secret via pointing the token URL at an attacker-controlled endpoint and triggering validation.. Mattermost Advisory ID: MMSA-2026-00761
Affected products
- Mattermost: from 11.7.0 before 11.7.11; from 11.8.0 before 11.8.6; from 11.9.0 before 11.9.2; from 11.10.0 before 11.10.2 — fixed in 11.7.11, 11.8.6, 11.9.2, 11.10.2
- Mattermost: from 11.9.0 through 11.9.1; from 11.8.0 through 11.8.5; from 11.7.0 through 11.7.10; from 11.10.0 through 11.10.1
How to fix
Upgrade to a fixed version: Mattermost 11.7.11, 11.8.6, 11.9.2, 11.10.2. Check the vendor advisory for mitigations.
References
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