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CVE-2026-93849— Mattermost allows authenticated users to trigger excessive memory allocation via crafted msgpack binary WebSocket frames

Quick assessment

Affected
Mattermost Mattermost
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mattermost 版本 11.9.x（≤ 11.9.1）、11.8.x（≤ 11.8.5）、11.7.x（≤ 11.7.10）以及 11.10.x（≤ 11.10.1）存在漏洞：其 WebSocket msgpack 解码器在字节字符串解码路径中未能实施内存分配限制。这使得经过身份验证的远程攻击者能够构造恶意二进制 WebSocket 帧，声明 Bin32 载荷长度高达 4,294,967,295 字节，从而引发服务器内存过度分配。 Mattermost 安全公告编号：MMSA-2026-00768

CVSS 6.5 · Medium EPSS 0.46% · P39

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 9

VendorProduct Version RangeStatus
Mattermost Mattermost 11.9.0≤ 11.9.1 affected
11.8.0≤ 11.8.5 affected
11.7.0≤ 11.7.10 affected
11.10.0≤ 11.10.1 affected
11.11.0 unaffected
11.9.2 unaffected
11.8.6 unaffected
11.7.11 unaffected
… +1 more rows
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I. Basic Information for CVE-2026-93849

Vulnerability Information
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Vulnerability Title
Mattermost allows authenticated users to trigger excessive memory allocation via crafted msgpack binary WebSocket frames
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 Mattermost fail to apply allocation limits to the byte-string decode paths in its WebSocket msgpack decoder, which allows an authenticated remote attacker to cause excessive server memory allocation via a crafted binary WebSocket frame declaring a Bin32 payload length of up to 4,294,967,295 bytes.. Mattermost Advisory ID: MMSA-2026-00768
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未经控制的内存分配
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mattermost Mattermost 11.9.0 ~ 11.9.1 -

II. Public POCs for CVE-2026-93849

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III. Intelligence Information for CVE-2026-93849

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Same Patch Batch · Mattermost · 2026-10-26 · 6 CVEs total

CVE-2026-116516 6.5 MEDIUM Insufficient length validation when parsing Zoom chat transcriptions
CVE-2026-93850 6.5 MEDIUM Unbounded memory consumption during PDF text extraction
CVE-2026-93846 3.8 LOW Team admin can escalate a team member's permissions via the team member roles endpoint
CVE-2026-93847 3.5 LOW Improper post type validation on scheduled post endpoints
CVE-2026-93848 2.7 LOW Mattermost OpenID discovery endpoint request bypasses outbound connection filtering, allow

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-789