CVE-2026-5740— Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server
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-2026-5740
Vulnerability Information
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Vulnerability Title
Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server
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 properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
未经控制的内存分配
Source: NVD (National Vulnerability Database)
Vulnerability Title
Mattermost 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司的一个开源协作平台。 Mattermost 11.6.0及之前的11.6.x版本、11.5.3及之前的11.5.x版本、11.4.4及之前的11.4.x版本和10.11.14及之前的10.11.x版本存在安全漏洞，该漏洞源于未正确验证msgpack编码的WebSocket帧，可能导致未经身份验证的远程攻击者通过特制二进制WebSocket消息崩溃服务器进程，造成完全服务中断。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Mattermost | Mattermost | 11.6.0 ~ 11.6.0 | - |
II. Public POCs for CVE-2026-5740
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · Mattermost · 2026-05-22 · 8 CVEs total
| 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-2026-4646 | 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-2026-6957
Path traversal in Mattermost Legal Hold plugin via unsanitiz - CVE-2026-4915
Server panic via outgoing webhook responses - CVE-2026-28735
GitHub OAuth Scope Validation - CVE-2026-4635
Persistent notification timing attack causing server denial - CVE-2026-3473
Improper file ownership validation in the Boards API allows
Same vendor: Mattermost
- CVE-2026-6957
Path traversal in Mattermost Legal Hold plugin via unsanitiz - CVE-2026-4915
Server panic via outgoing webhook responses - CVE-2026-28735
GitHub OAuth Scope Validation - CVE-2026-4635
Persistent notification timing attack causing server denial - CVE-2026-3473
Improper file ownership validation in the Boards API allows
Same weakness: CWE-789
- CVE-2026-9538
Archive::Tar versions before 3.10 for Perl allow memory exha - CVE-2018-25378
Notebook Pro 2.0 Denial of Service via Notebook Name Field - CVE-2018-25368
Nord VPN 6.14.31 Denial of Service via Password Field - CVE-2026-8485
Uncontrolled Memory Allocation vulnerability in Progress Sof - CVE-2026-47313
SAMSUNG Escargot 安全漏洞
V. Comments for CVE-2026-5740
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