Mattermost Mobile App: SSO Callback Origin Validation Bypass (<=2.37, 11.x)
CVE-2026-22880 Published on May 21, 2026
Mobile SSO authentication flow allows credential theft via malicious server
Mattermost Mobile Apps versions <=2.37 11.4 2.0.37 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to properly validate the SSO authentication callback origin which allows an attacker controlling a malicious Mattermost server to steal user credentials for a legitimate Mattermost server via relaying the SSO code exchange flow through the mobile application. Mattermost Advisory ID: MMSA-2025-00564
Vulnerability Analysis
CVE-2026-22880 is exploitable with network access, requires user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality, with no impact on integrity and availability.
Weakness Type
What is a Session Riding Vulnerability?
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request. When a web server is designed to receive a request from a client without any mechanism for verifying that it was intentionally sent, then it might be possible for an attacker to trick a client into making an unintentional request to the web server which will be treated as an authentic request. This can be done via a URL, image load, XMLHttpRequest, etc. and can result in exposure of data or unintended code execution.
CVE-2026-22880 has been classified to as a Session Riding vulnerability or weakness.
Products Associated with CVE-2026-22880
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Affected Versions
Mattermost:- Before and including 2.0.37 is affected.
- Before and including 11.0.4 is affected.
- Before and including 11.1.3 is affected.
- Before and including 11.3.2 is affected.
- Before and including 10.11.11 is affected.
- Version 2.38.0 is unaffected.
- Version 11.5.0 is unaffected.
- Version 2.37.1.0 is unaffected.
- Version 11.4.1 is unaffected.
- Version 11.3.2 is unaffected.
- Version 11.2.4 is unaffected.
- Version 10.11.12 is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.