CVE-2026-19541 PUBLISHED

Outgoing OAuth connection client secret exposure during connection validation

Assigner: Mattermost
Reserved: 11.08.2026 Published: 16.10.2026 Updated: 16.10.2026

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

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CVSS Score: 6.5

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	Low	Integrity Impact	None
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.9.0 to 11.9.1 (incl.) affected from 11.8.0 to 11.8.5 (incl.) affected from 11.7.0 to 11.7.10 (incl.) affected from 11.10.0 to 11.10.1 (incl.) Version 11.11.0 is unaffected Version 11.9.2 is unaffected Version 11.8.6 is unaffected Version 11.7.11 is unaffected Version 11.10.2 is unaffected

Solutions

Update Mattermost to versions 11.11.0, 11.9.2, 11.8.6, 11.7.11, 11.10.2 or higher.

Credits

Juho Forsén finder

References

MMSA-2026-00761

Problem Types

CWE-201: Insertion of Sensitive Information Into Sent Data CWE