CVE-2026-61709

OpenFGA is an authorization and permission engine built for developers. Prior to 1.18.1, the ListUsers API could return a user that should have been excluded when an authorization relation used an intersection containing a base but not excluded operand, the base was granted through a type-bound public wildcard, and the excluded user also had a concrete tuple through another intersection operand. In pkg/server/commands/listusers/list_users_rpc.go, expandIntersection counted the concrete tuple and wildcard without first rejecting entries in excludedUsersMap. Applications that used ListUsers to enumerate or enforce access could therefore treat an excluded user as authorized. This issue is fixed in version 1.18.1.

OpenFGA is an authorization and permission engine built for developers. Prior to 1.18.1, the ListUsers API could return a user that should have been excluded when an authorization relation used an intersection containing a base but not excluded operand, the base was granted through a type-bound public wildcard, and the excluded user also had a concrete tuple through another intersection operand. In pkg/server/commands/listusers/list_users_rpc.go, expandIntersection counted the concrete tuple and wildcard without first rejecting entries in excludedUsersMap. Applications that used ListUsers to enumerate or enforce access could therefore treat an excluded user as authorized. This issue is fixed in version 1.18.1.

Description

In OpenFGA, the ListUsers API could incorrectly return a user who should have been excluded.

Preconditions

This applies if all of the following are present:

• The authorization model contains a relation defined as an intersection (and) where at least one operand is an exclusion of the form base but not excluded: e.g. rel1: (public_user but not blocked) and rel2
• The base side of that exclusion is granted through a type-bound public wildcard (e.g. user:*).
• A user excluded by the but not clause is also granted, via a concrete tuple, through another operand of the intersection.
• Your application uses ListUsers to enumerate or enforce access

Fix

Upgrade to OpenFGA v1.18.1 or greater.

Acknowledgements

OpenFGA would like to thank @5ud0er for the detailed report.

OpenFGA is an authorization and permission engine built for developers. Prior to 1.18.1, the ListUsers API could return a user that should have been excluded when an authorization relation used an intersection containing a base but not excluded operand, the base was granted through a type-bound public wildcard, and the excluded user also had a concrete tuple through another intersection operand. In pkg/server/commands/listusers/list_users_rpc.go, expandIntersection counted the concrete tuple and wildcard without first rejecting entries in excludedUsersMap. Applications that used ListUsers to enumerate or enforce access could therefore treat an excluded user as authorized. This issue is fixed in version 1.18.1.

OpenFGA is an authorization and permission engine built for developers. Prior to 1.18.1, the ListUsers API could return a user that should have been excluded when an authorization relation used an intersection containing a base but not excluded operand, the base was granted through a type-bound public wildcard, and the excluded user also had a concrete tuple through another intersection operand. In pkg/server/commands/listusers/list_users_rpc.go, expandIntersection counted the concrete tuple and wildcard without first rejecting entries in excludedUsersMap. Applications that used ListUsers to enumerate or enforce access could therefore treat an excluded user as authorized. This issue is fixed in version 1.18.1.

Description

In OpenFGA, the ListUsers API could incorrectly return a user who should have been excluded.

Preconditions

This applies if all of the following are present:

• The authorization model contains a relation defined as an intersection (and) where at least one operand is an exclusion of the form base but not excluded: e.g. rel1: (public_user but not blocked) and rel2
• The base side of that exclusion is granted through a type-bound public wildcard (e.g. user:*).
• A user excluded by the but not clause is also granted, via a concrete tuple, through another operand of the intersection.
• Your application uses ListUsers to enumerate or enforce access

Fix

Upgrade to OpenFGA v1.18.1 or greater.

Acknowledgements

OpenFGA would like to thank @5ud0er for the detailed report.