Mattermost up to 10.11.10/11.2.2/11.3.0 Websocket Message improper validation of specified type of input

Summaryinfo

A vulnerability was found in Mattermost up to 10.11.10/11.2.2/11.3.0. It has been classified as problematic. The affected element is an unknown function of the component Websocket Message Handler. The manipulation leads to improper validation of specified type of input. This vulnerability is referenced as CVE-2026-2454. Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Mattermost up to 10.11.10/11.2.2/11.3.0. This issue affects an unknown code block of the component Websocket Message Handler. The manipulation with an unknown input leads to a improper validation of specified type of input vulnerability. Using CWE to declare the problem leads to CWE-1287. The product receives input that is expected to be of a certain type, but it does not validate or incorrectly validates that the input is actually of the expected type. Impacted is availability. The summary by CVE is:

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to handle incorrectly reported array lengths which allows malicious user to cause OOM errors and crash the server via sending corrupted msgpack frames within websocket messages to calls plugin. Mattermost Advisory ID: MMSA-2025-00537

It is possible to read the advisory at mattermost.com. The identification of this vulnerability is CVE-2026-2454 since 02/13/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 10.11.11, 11.2.3, 11.3.1 or 11.4.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-12510). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Groupware Software

Name

• Mattermost

Version

• 10.11.0
• 10.11.1
• 10.11.2
• 10.11.3
• 10.11.4
• 10.11.5
• 10.11.6
• 10.11.7
• 10.11.8
• 10.11.9
• 10.11.10
• 11.0
• 11.1
• 11.2
• 11.2.0
• 11.2.1
• 11.2.2
• 11.3.0

License

• open-source

CPE 2.3info

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CPE 2.2info

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Entryinfo

Be aware that VulDB is the high quality source for vulnerability data.

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