CVE-2026-54733: Signature Bypass

Description

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.

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Weakness Type (CWE)

CWE-347 CWE-347

References

Other References

https://github.com/microsoft/o365-moodle/commit/01b2d4c2e13b06a66557527084cbf9bace655944 https://github.com/microsoft/o365-moodle/commit/258872f6e2011f4efa8ebb77d2898142a9435e89 https://github.com/microsoft/o365-moodle/commit/d5596655f0baaee0f11aec2e10d6f36b0bd29220 https://github.com/microsoft/o365-moodle/releases/tag/v20260423_m405 https://github.com/microsoft/o365-moodle/releases/tag/v20260423_m500 https://github.com/microsoft/o365-moodle/releases/tag/v20260423_m501 https://github.com/microsoft/o365-moodle/security/advisories/GHSA-hqjh-93qv-47v5

Frequently Asked Questions

What is CVE-2026-54733? +

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.

How do I check if I'm vulnerable to CVE-2026-54733? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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