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OpenFGA: ListUsers returns a deliberately-excluded user when a `but not` exclusion under a type-bound wildcard is intersected (`and`) with another relation that also grants that userGHSA-g3pg-frfm-pr2m

MEDIUMFix: openfga/openfga@171806c

GHSA-g3pg-frfm-pr2m is a medium-severity (CVSS 5.3) CWE-281 vulnerability in github.com/openfga/openfga. A fix is available for github.com/openfga/openfga — see the affected versions and patch details below.

Also known asCVE-2026-61709GO-2026-6488
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 31, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-g3pg-frfm-pr2m.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs29th percentile — riskier than 29% of all scored CVEsHighest risk
0.00%0.28%0.57%0.85%0.4%0.4%Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐹github.com/openfga/openfga

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/openfga/openfgaall versions1.18.1go get github.com/openfga/openfga@v1.18.1

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/openfga/openfga, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/openfga/openfga to 1.18.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g3pg-frfm-pr2m is resolved across your whole dependency graph.

  3. Workarounds

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This flaw is in OpenFGA's ListUsers API, which could return a user who should have been excluded by a but-not clause when an intersection used a type-bound public wildcard. Red Hat does not ship OpenFGA as a standalone product. The code is bundled in Grafana's experimental Zanzana authorization engine and Grafana is…

Workaround published by Red Hat
No product-side mitigation is required while Zanzana remains disabled, which is the default. If Zanzana has been turned on, do not use ListUsers results as an access-control decision; use Check for each user and object until Grafana vendors OpenFGA 1.18.1 or later.
Source: Red Hat security advisory for GHSA-g3pg-frfm-pr2m (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Hardened Imagesgrafana13-2-main-13.2.1-0.4.hum1RHSA-2026:67605
Red Hat Hardened Imagesgrafana12-4-main-12.4.10-0.5.hum1RHSA-2026:68777
Red Hat Hardened Imagesgrafana12-4-main-12.4.10-0.6.hum1RHSA-2026:68821
Red Hat Hardened Imagesgrafana13-1-main-13.1.6-0.3.hum1RHSA-2026:71040
Red Hat Hardened Imagesgrafana13-1-main-13.1.6-0.4.hum1RHSA-2026:72498

Frequently Asked Questions

### 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 in
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