CVE-2026-9597
Received Received - Intake

Session Hijacking in Mattermost via Magic-Link Token

Publication date: 2026-07-13

Last updated on: 2026-07-13

Assigner: Mattermost, Inc.

Description
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

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Meta Information

Published
2026-07-13
Last Modified
2026-07-13
Generated
2026-07-13
AI Q&A
2026-07-13
EPSS Evaluated
N/A
NVD
CVE-2026-9597
EUVD
EUVD-2026-43315

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
mattermost mattermost to 11.7.2 (inc)
mattermost mattermost to 11.6.4 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-305 The authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error.

Attack-Flow Graph

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Executive Summary

This vulnerability exists in Mattermost versions 11.7.x up to 11.7.2 and 11.6.x up to 11.6.4. It occurs because the system fails to verify whether a guest account has been deactivated before creating a session through the magic-link token login method. As a result, a guest user who has been deactivated can still obtain a fully functional session if they use a magic-link token that was issued before their account was deactivated.

Impact Analysis

The impact of this vulnerability is that a deactivated guest user can regain access to the system by using a previously issued magic-link token. This could allow unauthorized access to resources or information that should no longer be accessible to that user, potentially leading to information disclosure or unauthorized actions within the Mattermost environment.

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