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CVE-2026-10819— Mattermost Server Denial of Service via Animated GIF Emoji Upload

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是美国Mattermost公司开源的一个开源协作平台。 Mattermost 11.6.5及之前的11.6.x版本、10.11.20及之前的10.11.x版本、11.8.1及之前的11.8.x版本和11.7.4及之前的11.7.x版本存在资源管理错误漏洞，该漏洞源于未能限制动画GIF上传的帧数和文件大小，可能导致经过身份验证的攻击者通过上传特制动画GIF作为自定义表情符号造成拒绝服务。

CVSS 6.5 · Medium EPSS 0.42% · P35

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 9

VendorProduct Version RangeStatus
Mattermost Mattermost 11.6.0≤ 11.6.5 affected
10.11.0≤ 10.11.20 affected
11.8.0≤ 11.8.1 affected
11.7.0≤ 11.7.4 affected
11.9.0 unaffected
11.6.6 unaffected
10.11.21 unaffected
11.8.2 unaffected
… +1 more rows
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I. Basic Information for CVE-2026-10819

Vulnerability Information
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Vulnerability Title
Mattermost Server Denial of Service via Animated GIF Emoji Upload
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.6.x <= 11.6.5, 10.11.x <= 10.11.20, 11.8.x <= 11.8.1, 11.7.x <= 11.7.4 fail to limit the number of frames and enforce the file size cap on animated GIF uploads, which allows an authenticated attacker to cause a denial of service via a crafted animated GIF uploaded as a custom emoji.. Mattermost Advisory ID: MMSA-2026-00695
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
Vulnerability Title
Mattermost 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost 11.6.5及之前的11.6.x版本、10.11.20及之前的10.11.x版本、11.8.1及之前的11.8.x版本和11.7.4及之前的11.7.x版本存在资源管理错误漏洞，该漏洞源于未能限制动画GIF上传的帧数和文件大小，可能导致经过身份验证的攻击者通过上传特制动画GIF作为自定义表情符号造成拒绝服务。
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 ~ 11.6.5 -

II. Public POCs for CVE-2026-10819

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III. Intelligence Information for CVE-2026-10819

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IV. Related Vulnerabilities

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

V. Comments for CVE-2026-10819

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