Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to properly validate user identity in the OpenID {{IsSameUser()}} comparison logic, which allows an attacker to take over arbitrary user accounts via an overly permissive substring matching flaw in the user discovery flow.. Mattermost Advisory ID: MMSA-2026-00590
Metrics
Affected Vendors & Products
References
History
Thu, 26 Mar 2026 19:00:00 +0000
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| CPEs | cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | |
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Mattermost mattermost Server
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Thu, 26 Mar 2026 14:15:00 +0000
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ssvc
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Thu, 26 Mar 2026 12:00:00 +0000
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Mattermost
Mattermost mattermost |
Wed, 25 Mar 2026 16:45:00 +0000
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| Description | Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to properly validate user identity in the OpenID {{IsSameUser()}} comparison logic, which allows an attacker to take over arbitrary user accounts via an overly permissive substring matching flaw in the user discovery flow.. Mattermost Advisory ID: MMSA-2026-00590 | |
| Title | Account Takeover via Substring Matching in OpenID Connect Authentication | |
| Weaknesses | CWE-303 | |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: Mattermost
Published:
Updated: 2026-03-26T13:19:52.338Z
Reserved: 2026-02-23T22:07:32.808Z
Link: CVE-2026-27656
Updated: 2026-03-26T13:19:49.531Z
Status : Analyzed
Published: 2026-03-25T17:16:56.797
Modified: 2026-03-26T18:51:38.050
Link: CVE-2026-27656
No data.