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CVE-2026-15814— Uploading a crafted image causes excessive memory allocation in the Mattermost Server

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 ≤ 11.9.0、11.8.x ≤ 11.8.4、11.7.x ≤ 11.7.7 和 10.11.x ≤ 10.11.22 在解码上传的图像文件时，未能限制分配的内存量，这使得已认证的用户能够通过上传一张特制的图像文件作为个人头像、频道文件附件、团队图标或自定义品牌图像，导致服务器内存过度消耗，从而可能引发服务拒绝（DoS）。Mattermost 安全公告编号：MMSA-2026-00719

CVSS 6.5 · Medium
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I. Basic Information for CVE-2026-15814

Vulnerability Information
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Vulnerability Title
Uploading a crafted image causes excessive memory allocation in the Mattermost Server
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to limit the amount of memory allocated when decoding uploaded image files which allows an authenticated user to cause excessive server memory consumption and potential denial of service via uploading a specially crafted image as a profile picture, channel file attachment, team icon, or custom brand image. Mattermost Advisory ID: MMSA-2026-00719
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
对高度压缩数据的处理不恰当(数据放大攻击)
Source: CVE Program / CVE List V5

Affected Products

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

II. Public POCs for CVE-2026-15814

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III. Intelligence Information for CVE-2026-15814

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Same Patch Batch · Mattermost · 2026-09-14 · 11 CVEs total

CVE-2026-8821 7.1 HIGH Playbooks run owner channel membership permission bypass
CVE-2026-9812 6.5 MEDIUM Missing property field ownership validation in Playbooks run property update endpoint
CVE-2026-5132 6.5 MEDIUM Unbounded zlib decompression in Calls SDP WebSocket messages
CVE-2026-10556 5.3 MEDIUM Unauthenticated webhook request with null notification entry could crash the Microsoft Cal
CVE-2026-10542 5.0 MEDIUM Playbooks channel action update validation issue
CVE-2026-13417 4.3 MEDIUM Boards plugin denial of service via unvalidated block fields.properties
CVE-2026-14344 4.3 MEDIUM Inconsistent authorization checks in Mattermost Boards endpoints
CVE-2026-12882 4.3 MEDIUM Mattermost Markdown autolink parsing denial of service
CVE-2026-11993 4.3 MEDIUM Fix authenticated members disabling file content indexing server-wide via extraction pool
CVE-2026-14259 4.3 MEDIUM Board archive import bypasses team board creation permissions

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-409

V. Comments for CVE-2026-15814

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