by Kastro
Paper/Archive/CVE-2026-54733

CVE-2026-54733

microsoft o365-moodle — moodle-local_o365: Authentication bypass via unverified JWT signature in Teams SSO endpoint

EPSS 0.9%CVSS 9.3
critical.is priorityof 100
40
CVSS 9.3 (CNA)9.3 / 10 × 3027.9Not in CISA KEV+300.0EPSS percentile 59.0.590 × 2011.8No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
o365-moodle< 4.5.6–CNA
o365-moodle>= 5.0.0, < 5.0.5–CNA
o365-moodle>= 5.1.0, < 5.1.1–CNA

Scores by source

GitHub_M (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refgithub.com/microsoft/o365-moodle/security/advisories/GHSA-hqjh-93qv-47v5refgithub.com/microsoft/o365-moodle/commit/01b2d4c2e13b06a66557527084cbf9bace655944refgithub.com/microsoft/o365-moodle/commit/258872f6e2011f4efa8ebb77d2898142a9435e89refgithub.com/microsoft/o365-moodle/commit/d5596655f0baaee0f11aec2e10d6f36b0bd29220refgithub.com/microsoft/o365-moodle/releases/tag/v20260423_m405refgithub.com/microsoft/o365-moodle/releases/tag/v20260423_m500refgithub.com/microsoft/o365-moodle/releases/tag/v20260423_m501