CVE-2026-4646— Insufficient input validation in GitHub plugin API causes denial of service
Possible ATT&CK Techniques 1AI
T1496 · Resource HijackingAffected Version Matrix 9
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | 11.6.0≤ 11.6.0 | affected |
11.5.0≤ 11.5.3 | affected | ||
11.4.0≤ 11.4.4 | affected | ||
10.11.0≤ 10.11.14 | affected | ||
11.7.0 | unaffected | ||
11.6.1 | unaffected | ||
11.5.4 | unaffected | ||
11.4.5 | unaffected | ||
| … +1 more rows | |||
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I. Basic Information for CVE-2026-4646
Vulnerability Information
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Vulnerability Title
Insufficient input validation in GitHub plugin API causes denial of service
Source: NVD (National Vulnerability Database)
Vulnerability 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
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Source: NVD (National Vulnerability Database)
Vulnerability Type
CWE-1287
Source: NVD (National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Mattermost | Mattermost | 11.6.0 ~ 11.6.0 | - |
II. Public POCs for CVE-2026-4646
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · Mattermost · 2026-05-22 · 8 CVEs total
| CVE-2026-5740 | 7.5 HIGH | Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server |
| CVE-2026-4635 | 6.5 MEDIUM | Persistent notification timing attack causing server denial of service |
| CVE-2026-5755 | 6.5 MEDIUM | Denial of service via crafted TIFF file upload |
| CVE-2026-3473 | 5.9 MEDIUM | Improper file ownership validation in the Boards API allows unauthorised file access |
| CVE-2026-28735 | 5.4 MEDIUM | GitHub OAuth Scope Validation |
| CVE-2026-5308 | 4.9 MEDIUM | Missing request body size limits on Zoom plugin HTTP endpoints |
| CVE-2026-3636 | 4.3 MEDIUM | Sanitize team member data returned by API |
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Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-1287
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V. Comments for CVE-2026-4646
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