CVE-2026-54733
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.88%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 4.0
- 9.3 CRITICALCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.88% probability · 57th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-347
- Source
- security-advisories@github.com
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.