---
id: CVE-2026-16251
title: >-
  Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1,
  11.8.x <= 11.8.5 fail to limit the size of remote image responses buffered in
  memory during local image proxy direct fetches, which allows a remote attacker
  to c…
summary: >-
  Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1,
  11.8.x <= 11.8.5 fail to limit the size of remote image responses buffered in
  memory during local image proxy direct fetches, which allows a remote attacker
  to c…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-770
vendor: Mattermost
product: Mattermost
affected:
  - Mattermost >= 11.10.0 <= 11.10.0
  - Mattermost >= 11.7.0 <= 11.7.9
  - Mattermost >= 11.9.0 <= 11.9.1
  - Mattermost >= 11.8.0 <= 11.8.5
published: '2026-10-16'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T19:23:18.623'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-16251'
references:
  - url: 'https://mattermost.com/security-updates'
    label: responsibledisclosure@mattermost.com
tags:
  - nvd
  - cve.org
epss: 0.0028
epssPercentile: 0.20322
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-16T11:29:04.337536Z'
ingestedAt: '2026-10-16T08:02:23.119Z'
---

## Overview

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to limit the size of remote image responses buffered in memory during local image proxy direct fetches, which allows a remote attacker to cause memory exhaustion on the server via a crafted oversized image response.. Mattermost Advisory ID: MMSA-2026-00726

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.