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Vulnerability · Published Jul 16, 2026 · Assigned by GitHub_M

CVE-2026-54733moodle-local_o365: Authentication bypass via unverified JWT signature in Teams SSO endpoint

Critical 9.3

In plain English

A critical-severity security flaw in o365-moodle from microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 59% of all known vulnerabilities).

Severity (CVSS 4.0)9.3Critical
Exploit odds (30 days)0.9%top 40.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
microsoft o365-moodle < 4.5.6>= 5.0.0, < 5.0.5>= 5.1.0, < 5.1.1

Weakness: CWE-347 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References