Canonical authd up to 0.7.0 User Identity Matching manager.go UpdateUser improper authentication

Summaryinfo

A vulnerability categorized as very critical has been discovered in Canonical authd up to 0.7.0. This affects the function UpdateUser of the file internal/users/manager.go of the component User Identity Matching. Executing a manipulation can lead to improper authentication. This vulnerability is handled as CVE-2026-102631. The attack can be executed remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Canonical authd up to 0.7.0 and classified as very critical. This vulnerability affects the function UpdateUser of the file internal/users/manager.go of the component User Identity Matching. The manipulation with an unknown input leads to a improper authentication vulnerability. The CWE definition for the vulnerability is CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In authd before 0.7.1, the user identity matching in UpdateUser (internal/users/manager.go) resolves an incoming login by the broker-scoped provider ID, but falls back to matching the username when the provider ID does not belong to any known user, and does not reject a conflicting non-empty provider ID. If an identity provider reassigns an email address, which authd uses as the username, to a new account, the new account inherits the previous user's local UID and home directory on its next login. This allows the new user to access and modify files belonging to the previous user, including credentials such as SSH keys and cloud API tokens, and silently rebinds the local account record to the new identity. As a mitigation, administrators should lock or delete the previous user's local authd account when the corresponding IdP account is removed.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-102631 since 09/29/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/15/2026).

Upgrading to version 0.7.1, 0.7.1~ubuntu24.04.1 or 0.7.1~ubuntu26.04 eliminates this vulnerability.

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Productinfo

Vendor

• Canonical

Name

• authd

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7.0

License

• open-source

Website

• Product: https://github.com/canonical/authd/

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