microsoft o365-moodle up to 4.5.5/5.0.4/5.1.0 Teams SSO Endpoint sso_login.php upn improper authentication

Summaryinfo

A vulnerability, which was classified as critical, was found in microsoft o365-moodle up to 4.5.5/5.0.4/5.1.0. This impacts an unknown function of the file sso_login.php of the component Teams SSO Endpoint. The manipulation of the argument upn results in improper authentication. This vulnerability is reported as CVE-2026-54733. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, was found in microsoft o365-moodle up to 4.5.5/5.0.4/5.1.0. Affected is some unknown functionality of the file sso_login.php of the component Teams SSO Endpoint. The manipulation of the argument upn with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

The Microsoft 365 and Microsoft Entra ID Plugins for Moodle provide Office 365 and Azure Active Directory integration for Moodle. Prior to 4.5.6, 5.0.5, and 5.1.1, the Microsoft Office 365 Integration plugin local_o365 Teams SSO endpoint sso_login.php base64-decodes a JWT payload and authenticates users from the upn claim without verifying the JWT signature, allowing an unauthenticated attacker to forge a token and obtain a Moodle session as an O365-authenticated user. This issue is fixed in versions 4.5.6, 5.0.5, and 5.1.1.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-54733 since 06/16/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 07/16/2026).

By approaching the search of inurl:sso_login.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 4.5.6, 5.0.5 or 5.1.1 eliminates this vulnerability.

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Productinfo

Type

• Learning Management Software

Vendor

• microsoft

Name

• o365-moodle

Version

• 4.5.0
• 4.5.1
• 4.5.2
• 4.5.3
• 4.5.4
• 4.5.5
• 5.0
• 5.0.0
• 5.0.1
• 5.0.2
• 5.0.3
• 5.0.4
• 5.1.0

License

• commercial

Website

• Vendor: https://www.microsoft.com/
• Product: https://github.com/microsoft/o365-moodle/

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