nOAuth

Summary

Descope identified a possible misconfiguration in Azure AD which could lead to misuse of the "Log in with Microsoft" authentication method on a web app. If an application relies on email attribute claims for authentication (which is against best practice) and also merges user accounts without proper validation, an attacker could falsify an email claim to gain full control over the target account. Descope and Microsoft Microsoft identified several popular multi-tenant applications with users that used an email address with an unverified domain owner, which would therefore be vulnerable to this type of takeover. Following disclosure, Microsoft deployed mitigations to omit token claims from unverified domain owners for most applications.

Affected Services

Azure AD

Remediation

None required

Tracked CVEs

No tracked CVEs

References

Contributed by https://github.com/korniko98