---
id: CVE-2026-3495
title: >-
  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 so…
summary: >-
  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 so…
severity: low
cvss: 3.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-79
vendor: mattermost
product: mattermost_server
affected:
  - 'mattermost_server >= 10.11.0, < 10.11.14'
  - 'mattermost_server >= 11.5.0, < 11.5.2'
patched:
  - mattermost_server 11.5.2
published: '2026-05-18'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T20:10:00.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-3495'
references:
  - url: 'https://mattermost.com/security-updates'
    label: responsibledisclosure@mattermost.com
tags:
  - nvd
epss: 0.00242
epssPercentile: 0.14282
ingestedAt: '2026-10-14T20:53:12.295Z'
---

## Overview

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

## Affected

- `mattermost_server >= 10.11.0, < 10.11.14`
- `mattermost_server >= 11.5.0, < 11.5.2`

## Remediation

Upgrade past the affected range:

- `mattermost_server 11.5.2`