CVE-2026-3495

Unescaped variables during error page composition

Published May 18, 2026 CVSS 3.1 · 3.8 Low EPSS < 1% KEV · Not listed
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

Remediation

Vendor Solution

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

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-jx93-pf6x-874r Mattermost doesn't escape some variables that could contain malicious content during error page composition
References
History
Type Values Removed Values Added
First Time appeared Mattermost mattermost Server
CPEs cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Vendors & Products Mattermost mattermost Server
Type Values Removed Values Added
Metrics ssvc

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

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

Weaknesses

Sources

Status
PUBLISHED
Assigner
Mattermost
Published
Updated
May 18, 2026, 2:33 PM
Reserved
Mar 3, 2026, 5:33 PM
Status
Analyzed
Published
May 18, 2026, 8:16 AM
Modified
Oct 14, 2026, 8:10 PM