Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to escape some variables that could contain malicious content during error page composition which allows an attacker with access to edit some site configuration to execute some malicious code via injecting some JS as part of those values.. Mattermost Advisory ID: MMSA-2026-00622

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Fixes

Solution

Update Mattermost to versions 11.6.0, 11.5.2, 10.11.14 or higher.


Workaround

No workaround given by the vendor.

References
History

Mon, 18 May 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 18 May 2026 10:15:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Mon, 18 May 2026 08:00:00 +0000

Type Values Removed Values Added
Description Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to escape some variables that could contain malicious content during error page composition which allows an attacker with access to edit some site configuration to execute some malicious code via injecting some JS as part of those values.. Mattermost Advisory ID: MMSA-2026-00622
Title Unescaped variables during error page composition
Weaknesses CWE-79
References
Metrics cvssV3_1

{'score': 3.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-05-18T14:33:30.914Z

Reserved: 2026-03-03T17:33:56.666Z

Link: CVE-2026-3495

cve-icon Vulnrichment

Updated: 2026-05-18T14:33:26.384Z

cve-icon NVD

Status : Undergoing Analysis

Published: 2026-05-18T08:16:13.900

Modified: 2026-05-18T17:32:38.127

Link: CVE-2026-3495

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-18T10:00:12Z

Weaknesses