CVE-2026-4635— Persistent notification timing attack causing server denial of service
Possible ATT&CK Techniques 1AI
T1499 · Endpoint Denial of ServiceAffected 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-2026-4635
Vulnerability Information
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Vulnerability Title
Persistent notification timing attack causing server 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 archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel.. Mattermost Advisory ID: MMSA-2026-00637
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:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
使用共享资源的并发执行不恰当同步问题(竞争条件)
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-2026-4635
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POCPremium
No public POC found.
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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-2026-5755 | 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-2026-4646 | 4.3 MEDIUM | Insufficient input validation in GitHub plugin API causes denial of service |
| CVE-2026-3636 | 4.3 MEDIUM | Sanitize team member data returned by API |
IV. Related Vulnerabilities
Same product: Mattermost
- CVE-2026-28735
GitHub OAuth Scope Validation - CVE-2026-3473
Improper file ownership validation in the Boards API allows - CVE-2026-4646
Insufficient input validation in GitHub plugin API causes de - CVE-2026-3636
Sanitize team member data returned by API - CVE-2026-5740
Unauthenticated WebSocket binary frame causes denial of serv
Same vendor: Mattermost
- CVE-2026-28735
GitHub OAuth Scope Validation - CVE-2026-3473
Improper file ownership validation in the Boards API allows - CVE-2026-4646
Insufficient input validation in GitHub plugin API causes de - CVE-2026-3636
Sanitize team member data returned by API - CVE-2026-5740
Unauthenticated WebSocket binary frame causes denial of serv
Same weakness: CWE-362
V. Comments for CVE-2026-4635
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