How severe is CVE-2026-39976?

CVE-2026-39976 has a CVSS score of 7.1/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-39976?

CVE-2026-39976 affects the following packages: laravel/passport (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-39976?

Update laravel/passport to 13.7.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39976 is resolved across your whole dependency graph.

How do I detect CVE-2026-39976 in my Packagist dependencies?

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

How do I mitigate CVE-2026-39976 if there is no patch (or I can't update yet)?

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.

Is CVE-2026-39976 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-39976 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-39976?

CVE-2026-39976 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 22th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-39976?

CVE-2026-39976 is classified as Improper Authentication (CWE-287). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-39976 published, and has it been updated?

CVE-2026-39976 was published on April 9, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

HIGH severity

CVE-2026-39976 — passport

HIGHFix: laravel/passport#1901

CVE-2026-39976 is a high-severity (CVSS 7.1) Improper Authentication vulnerability in laravel/passport. A fix is available for laravel/passport — see the affected versions and patch details below.

Laravel Passport's TokenGuard Authenticates Unrelated User for Client Credentials Tokens

Also known asGHSA-349c-2h2f-mxf6

Published

Apr 9, 2026

Updated

Oct 28, 2026

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 CVE-2026-39976.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk-0.11%

Lower risk than most CVEs22th percentile — riskier than 22% of all scored CVEsHighest risk

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

🐘laravel/passport

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

Description

Impact

Authentication Bypass for client_credentials tokens. the league/oauth2-server library sets the JWT sub claim to the client identifier (since there's no user). The token guard then passes this value to retrieveById() without validating it's actually a user identifier, potentially resolving an unrelated real user. Any machine-to-machine token can inadvertently authenticate as an actual user.

Usage of EnsureClientIsResourceOwner middleware together with Passport::$clientUuids set to false, can result in resolving the user instead, as stated in the documentation.

The underlying OAuth2 server sets the token's sub claim to the client's identifier for client credentials tokens. By default, Passport uses UUIDs for clients, so this cannot collide with a user's integer primary key. However, if you have set Passport::$clientUuids to false, a client credentials token may inadvertently resolve a user whose ID matches the client's ID. In such cases, using this middleware cannot guarantee that the incoming token is a client credentials token.

Patches

Patched in v13.7.1

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading? Disallow usage of client_credentials.

References

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`laravel/passport`	≥ 13.0.0&&< 13.7.1	13.7.1`composer require laravel/passport:^13.7.1`

Affected Products

1 product · 1 configurations

Application

passportlaravel

≥ 13.0.0 && < 13.7.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for laravel/passport, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update laravel/passport to 13.7.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39976 is resolved across your whole dependency graph.
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.

Frequently Asked Questions

### Impact Authentication Bypass for `client_credentials` tokens. the league/oauth2-server library sets the JWT sub claim to the client identifier (since there's no user). The token guard then passes this value to retrieveById() without validating it's actually a user identifier, potentially resolving an unrelated real user. Any machine-to-machine token can inadvertently authenticate as an actual user. Usage of `EnsureClientIsResourceOwner` middleware together with `Passport::$clientUuids` set to `false`, can result in resolving the user instead, as stated in the [documentation](https://lara