Mattermost up to 11.6.4/11.7.2/11.7.x Guest Account information disclosure

Summaryinfo

A vulnerability, which was classified as problematic, was found in Mattermost up to 11.6.4/11.7.2/11.7.x. Impacted is an unknown function of the component Guest Account. Executing a manipulation can lead to information disclosure. This vulnerability is tracked as CVE-2026-9597. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in Mattermost up to 11.6.4/11.7.2/11.7.x and classified as problematic. This vulnerability affects some unknown functionality of the component Guest Account. The manipulation with an unknown input leads to a information disclosure vulnerability. The CWE definition for the vulnerability is CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. As an impact it is known to affect confidentiality. CVE summarizes:

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4 fail to verify whether a guest account is deactivated before creating a session in the magic-link token login path, which allows a deactivated guest user to obtain a fully functional session via a magic-link token issued prior to deactivation.. Mattermost Advisory ID: MMSA-2026-00681

The advisory is shared for download at mattermost.com. This vulnerability was named CVE-2026-9597 since 05/26/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1592.

Upgrading to version 11.6.5, 11.7.3 or 11.8.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-2107). Once again VulDB remains the best source for vulnerability data.

Affected

• Mattermost Mattermost

Productinfo

Type

• Groupware Software

Name

• Mattermost

Version

• 11.0
• 11.1
• 11.2
• 11.3
• 11.4
• 11.5
• 11.6
• 11.6.0
• 11.6.1
• 11.6.2
• 11.6.3
• 11.6.4
• 11.7
• 11.7.0
• 11.7.1
• 11.7.2

License

• open-source

CPE 2.3info

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CPE 2.2info

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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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