---
id: CVE-2026-16251
title: >-
  Mattermost local image proxy allows server memory exhaustion via unbounded
  image response buffering
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'
cvssSource: cna
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
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-16T11:29:04.337536Z'
published: '2026-10-16'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T11:57:33.968Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-16251'
references:
  - url: 'https://mattermost.com/security-updates'
    label: MMSA-2026-00726
tags:
  - cve.org
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

## 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`

## Remediation

Update Mattermost to versions 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 or higher.