CVE-2026-16251
Awaiting Analysis Awaiting Analysis - Queue

Memory Exhaustion in Mattermost via Oversized Image Response

Publication date: 2026-10-16

Last updated on: 2026-10-16

Assigner: Mattermost, Inc.

Description
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

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-10-16
Last Modified
2026-10-16
Generated
2026-10-19
AI Q&A
2026-10-16
EPSS Evaluated
2026-10-18
NVD
CVE-2026-16251
EUVD
EUVD-2026-102750

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
Mattermost Mattermost 11.10.0
Mattermost Mattermost 11.7.0
Mattermost Mattermost 11.9.0
Mattermost Mattermost 11.8.0

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

Mattermost versions between 11.7.x and 11.10.x fail to restrict the size of remote images fetched during local image proxy operations. This allows attackers to send oversized images that consume excessive server memory, leading to potential denial of service.

Detection Guidance

The vulnerability involves memory exhaustion due to oversized image responses during local image proxy fetches. Monitor server memory usage and network traffic for unusually large image downloads. Check Mattermost server logs for failed or slow image proxy requests. Ensure your Mattermost version is updated beyond the affected ranges (11.10.0, 11.7.9, 11.9.1, 11.8.5).

Impact Analysis

If exploited, this vulnerability could cause the Mattermost server to run out of memory, resulting in service disruption or crashes. Users may experience downtime or inability to access the platform during an attack.

Compliance Impact

The vulnerability could lead to memory exhaustion on the server due to unchecked image response sizes, potentially causing service disruptions or crashes. This may impact compliance with GDPR or HIPAA by failing to ensure availability of systems processing personal or health data, as required under these regulations.

Mitigation Strategies

Update Mattermost to a version that fixes this vulnerability. Specifically, upgrade to versions beyond 11.10.0, 11.9.1, 11.8.5, or 11.7.9 depending on your current installation.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-16251. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart