{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata — refreshed continuously.","feed_url":"https://feed.craftedsignal.io/tags/cve-2026-39976/","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cves":[{"cvss":7.1,"id":"CVE-2026-39976"}],"_cs_exploited":false,"_cs_products":[],"_cs_severities":["high"],"_cs_tags":["cve-2026-39976","laravel","oauth2","authentication bypass"],"_cs_type":"advisory","_cs_vendors":[],"content_html":"\u003cp\u003eLaravel Passport, an OAuth2 server implementation for Laravel, is vulnerable to an authentication bypass (CVE-2026-39976) in versions 13.0.0 up to, but not including, 13.7.1. The vulnerability stems from the \u003ccode\u003eleague/oauth2-server\u003c/code\u003e library, where the JWT \u003ccode\u003esub\u003c/code\u003e claim is set to the client identifier for \u003ccode\u003eclient_credentials\u003c/code\u003e tokens, as there is no associated user. Subsequently, the token guard uses this client identifier to retrieve user information via \u003ccode\u003eretrieveById()\u003c/code\u003e without proper validation, potentially resolving and authenticating an unrelated, real user. This means any machine-to-machine token can inadvertently authenticate as an actual user within the Laravel application. The vulnerability is resolved in Laravel Passport version 13.7.1. This allows attackers to perform actions with the privileges of the authenticated user.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAttacker obtains a valid \u003ccode\u003eclient_credentials\u003c/code\u003e token issued by Laravel Passport (versions 13.0.0 - 13.7.0). This could be a token intended for machine-to-machine communication.\u003c/li\u003e\n\u003cli\u003eThe attacker sends a request to a protected endpoint of the Laravel application, including the \u003ccode\u003eclient_credentials\u003c/code\u003e token in the \u003ccode\u003eAuthorization\u003c/code\u003e header.\u003c/li\u003e\n\u003cli\u003eThe Laravel Passport token guard extracts the JWT \u003ccode\u003esub\u003c/code\u003e claim from the token. In vulnerable versions, this \u003ccode\u003esub\u003c/code\u003e claim contains the client identifier.\u003c/li\u003e\n\u003cli\u003eThe token guard calls \u003ccode\u003eretrieveById()\u003c/code\u003e using the client identifier from the \u003ccode\u003esub\u003c/code\u003e claim as the user ID.\u003c/li\u003e\n\u003cli\u003eDue to the lack of validation, \u003ccode\u003eretrieveById()\u003c/code\u003e queries the user database, potentially finding a user whose ID matches the client identifier.\u003c/li\u003e\n\u003cli\u003eIf a user with the matching ID is found, the application authenticates the request as that user, granting the attacker their privileges.\u003c/li\u003e\n\u003cli\u003eThe attacker can then access resources and perform actions as the authenticated user.\u003c/li\u003e\n\u003cli\u003eThe attacker exploits the user\u0026rsquo;s privileges to compromise data or perform unauthorized actions within the application.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of CVE-2026-39976 allows attackers to bypass authentication and gain unauthorized access to user accounts in Laravel applications using affected versions of Laravel Passport. This can lead to data breaches, privilege escalation, and other malicious activities, depending on the privileges of the compromised user accounts. The severity of the impact depends on the application\u0026rsquo;s functionality and the sensitivity of the data it handles. Potentially all applications using Laravel Passport for authentication are vulnerable.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUpgrade Laravel Passport to version 13.7.1 or later to patch CVE-2026-39976.\u003c/li\u003e\n\u003cli\u003eImplement additional validation within the application\u0026rsquo;s authentication logic to verify that the user ID extracted from the JWT \u003ccode\u003esub\u003c/code\u003e claim corresponds to a valid user, especially when using \u003ccode\u003eclient_credentials\u003c/code\u003e tokens.\u003c/li\u003e\n\u003cli\u003eMonitor application logs for unexpected authentication events or API requests originating from machine-to-machine tokens that are being authenticated as users. The \u003ccode\u003ewebserver\u003c/code\u003e log source can be used for this monitoring.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule provided to detect requests to protected endpoints with \u003ccode\u003eclient_credentials\u003c/code\u003e tokens that are incorrectly authenticated as users.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2026-04-09T17:16:31Z","date_published":"2026-04-09T17:16:31Z","id":"/briefs/2026-04-laravel-auth-bypass/","summary":"Laravel Passport versions 13.0.0 before 13.7.1 contain an authentication bypass vulnerability (CVE-2026-39976) where machine-to-machine tokens can authenticate as a real user due to improper validation of the JWT sub claim.","title":"Laravel Passport Authentication Bypass Vulnerability (CVE-2026-39976)","url":"https://feed.craftedsignal.io/briefs/2026-04-laravel-auth-bypass/"}],"language":"en","title":"CraftedSignal Threat Feed — Cve-2026-39976","version":"https://jsonfeed.org/version/1.1"}