Mattermost up to 11.7.9/11.8.5/11.9.1/11.10.0 Image Proxy memory allocation

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Mattermost up to 11.7.9/11.8.5/11.9.1/11.10.0. This issue affects some unknown processing of the component Image Proxy. The manipulation leads to memory allocation. This vulnerability is referenced as CVE-2026-16251. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Mattermost up to 11.7.9/11.8.5/11.9.1/11.10.0 and classified as problematic. This issue affects an unknown functionality of the component Image Proxy. The manipulation with an unknown input leads to a memory allocation vulnerability. Using CWE to declare the problem leads to CWE-789. The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated. Impacted is availability. The summary by CVE is:

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

The advisory is shared at mattermost.com. The identification of this vulnerability is CVE-2026-16251 since 07/20/2026. The exploitation is known to be easy. The attack may be initiated remotely. The exploitation requires an enhanced level of successful authentication. Neither technical details nor an exploit are publicly available.

Upgrading to version 11.7.10, 11.8.6, 11.9.2, 11.10.1 or 11.11.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-102750). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Groupware Software

Name

• Mattermost

Version

• 11.0
• 11.1
• 11.2
• 11.3
• 11.4
• 11.5
• 11.6
• 11.7
• 11.7.0
• 11.7.1
• 11.7.2
• 11.7.3
• 11.7.4
• 11.7.5
• 11.7.6
• 11.7.7
• 11.7.8
• 11.7.9
• 11.8
• 11.8.0
• 11.8.1
• 11.8.2
• 11.8.3
• 11.8.4
• 11.8.5
• 11.9
• 11.9.0
• 11.9.1
• 11.10.0

License

• open-source

CPE 2.3info

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CPE 2.2info

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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