CVE-2026-4646 PUBLISHED

Insufficient input validation in GitHub plugin API causes denial of service

Assigner: Mattermost
Reserved: 23.03.2026 Published: 22.05.2026 Updated: 22.05.2026

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint.. Mattermost Advisory ID: MMSA-2026-00638

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CVSS Score: 4.3

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

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.6.0 to 11.6.0 (incl.) affected from 11.5.0 to 11.5.3 (incl.) affected from 11.4.0 to 11.4.4 (incl.) affected from 10.11.0 to 10.11.14 (incl.) Version 11.7.0 is unaffected Version 11.6.1 is unaffected Version 11.5.4 is unaffected Version 11.4.5 is unaffected Version 10.11.15 is unaffected

Solutions

Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher.

Credits

Mariusz Maik finder

References

MMSA-2026-00638

Problem Types

CWE-1287: Improper Validation of Specified Type of Input CWE