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

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00172.

Exploitation none

Automatable no

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Mattermost Mattermost unaffected
Version Status Constraints
11.6.0 affected ≤ 11.6.0
11.5.0 affected ≤ 11.5.3
11.4.0 affected ≤ 11.4.4
10.11.0 affected ≤ 10.11.14
11.7.0 unaffected —
11.6.1 unaffected —
11.5.4 unaffected —
11.4.5 unaffected —
10.11.15 unaffected —

No data.

No data.

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Vendors Products
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Project Subscriptions

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Advisories

No advisories yet.

Fixes

Solution

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

Workaround

No workaround given by the vendor.

References
Link Providers
https://mattermost.com/security-updates cve-icon
History

Fri, 22 May 2026 13:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Fri, 22 May 2026 13:15:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Fri, 22 May 2026 11:00:00 +0000

Type Values Removed Values Added
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
Title Insufficient input validation in GitHub plugin API causes denial of service
Weaknesses CWE-1287
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-05-22T12:13:19.526Z

Reserved: 2026-03-23T12:22:47.515Z

Link: CVE-2026-4646

cve-icon Vulnrichment

Updated: 2026-05-22T12:13:14.988Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-22T13:00:13Z

Weaknesses