CVE-2026-16251
Received Received - Intake

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

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Meta Information

Published
2026-10-16
Last Modified
2026-10-16
Generated
2026-10-16
AI Q&A
2026-10-16
EPSS Evaluated
N/A
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
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KEV
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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.

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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.

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.

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.

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