Mattermost up to 11.6.x Shared Channel filename path traversal

Summaryinfo

A vulnerability was found in Mattermost up to 10.11.15/10.11.16/11.5.4/11.6.1/11.6.x and classified as critical. This impacts an unknown function of the component Shared Channel Handler. Executing a manipulation of the argument filename can lead to path traversal. The identification of this vulnerability is CVE-2026-6961. The attack may be launched remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Mattermost up to 10.11.15/10.11.16/11.5.4/11.6.1/11.6.x. It has been declared as problematic. This vulnerability affects an unknown code of the component Shared Channel Handler. The manipulation of the argument filename with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect integrity, and availability. CVE summarizes:

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 Mattermost fails to sanitize FileInfo.Name received from federated peers during shared channel file sync, which allows an attacker who controls a federated server to write files to arbitrary locations within the target server's filestore via path traversal sequences in the filename field.. Mattermost Advisory ID: MMSA-2026-00661

The weakness was shared by Hassan Mohammed. The advisory is available at mattermost.com. This vulnerability was named CVE-2026-6961 since 04/24/2026. The exploitation appears to be easy. The attack can be initiated remotely. Additional levels of successful authentication are needed for exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1006 by the MITRE ATT&CK project.

Upgrading to version 10.11.16, 10.11.17, 11.5.5, 11.6.2 or 11.7.0 eliminates this vulnerability.

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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
• 10.11.11
• 10.11.12
• 10.11.13
• 10.11.14
• 10.11.15
• 10.11.16
• 11.0
• 11.1
• 11.2
• 11.3
• 11.4
• 11.5
• 11.5.0
• 11.5.1
• 11.5.2
• 11.5.3
• 11.5.4
• 11.6
• 11.6.0
• 11.6.1

License

• open-source

CPE 2.3info

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CPE 2.2info

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