Vulnerability · Published May 22, 2026 · Assigned by Mattermost
CVE-2026-4646Insufficient input validation in GitHub plugin API causes denial of service
Medium 4.3
In plain English
A medium-severity security flaw in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 16% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-plugin-github | 1.0.1-0.20260330164815-c2840e980b3c | GO-2026-5833 |
| Go | github.com/mattermost/mattermost-plugin-github | 1.0.1-0.20260330164815-c2840e980b3c | GHSA-rmvv-8v8w-rf7x |
| Go | github.com/mattermost/mattermost-server | 11.4.5 | GHSA-rmvv-8v8w-rf7x |
| Go | github.com/mattermost/mattermost-server | 11.6.1 | GHSA-rmvv-8v8w-rf7x |
| Go | github.com/mattermost/mattermost-server | 10.11.15+incompatible, 11.4.5+incompatible, 11.5.4+incompatible, 11.6.1+incompatible | GO-2026-5833 |
| Go | github.com/mattermost/mattermost-server | 10.11.15 | GHSA-rmvv-8v8w-rf7x |
| Go | github.com/mattermost/mattermost-server | 11.5.4 | GHSA-rmvv-8v8w-rf7x |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.6.0 – through 11.6.011.5.0 – through 11.5.311.4.0 – through 11.4.410.11.0 – through 10.11.14 |
Weakness: CWE-1287 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
References
- MMSA-2026-00638 vendor-advisory