Laravel — CraftedSignal Threat Feed

Laravel Passport Authentication Bypass Vulnerability (CVE-2026-39976)

hello@craftedsignal.io — Thu, 09 Apr 2026 17:16:31 +0000

Laravel 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 league/oauth2-server library, where the JWT sub claim is set to the client identifier for client_credentials tokens, as there is no associated user. Subsequently, the token guard uses this client identifier to retrieve user information via retrieveById() 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.

Attack Chain

Attacker obtains a valid client_credentials token issued by Laravel Passport (versions 13.0.0 - 13.7.0). This could be a token intended for machine-to-machine communication.
The attacker sends a request to a protected endpoint of the Laravel application, including the client_credentials token in the Authorization header.
The Laravel Passport token guard extracts the JWT sub claim from the token. In vulnerable versions, this sub claim contains the client identifier.
The token guard calls retrieveById() using the client identifier from the sub claim as the user ID.
Due to the lack of validation, retrieveById() queries the user database, potentially finding a user whose ID matches the client identifier.
If a user with the matching ID is found, the application authenticates the request as that user, granting the attacker their privileges.
The attacker can then access resources and perform actions as the authenticated user.
The attacker exploits the user’s privileges to compromise data or perform unauthorized actions within the application.

Impact

Successful 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’s functionality and the sensitivity of the data it handles. Potentially all applications using Laravel Passport for authentication are vulnerable.

Recommendation

Upgrade Laravel Passport to version 13.7.1 or later to patch CVE-2026-39976.
Implement additional validation within the application’s authentication logic to verify that the user ID extracted from the JWT sub claim corresponds to a valid user, especially when using client_credentials tokens.
Monitor application logs for unexpected authentication events or API requests originating from machine-to-machine tokens that are being authenticated as users. The webserver log source can be used for this monitoring.
Deploy the Sigma rule provided to detect requests to protected endpoints with client_credentials tokens that are incorrectly authenticated as users.

Sharp CMS Path Traversal Vulnerability (CVE-2026-33686)

hello@craftedsignal.io — Thu, 26 Mar 2026 22:16:31 +0000

Sharp CMS, a content management framework built for Laravel, is vulnerable to a path traversal attack. This vulnerability affects versions prior to 9.20.0 and stems from the FileUtil class not properly sanitizing file extensions. The flaw allows attackers to manipulate file paths by injecting path separators, potentially leading to unauthorized file access or manipulation within the storage layer. The vulnerability resides in the FileUtil::explodeExtension() function within…

Sharp Laravel Admin Panel Unrestricted File Upload Vulnerability

hello@craftedsignal.io — Wed, 25 Mar 2026 20:03:11 +0000

The code16/sharp Laravel admin panel package, specifically versions before 9.20.0, is vulnerable to unrestricted file upload. An authenticated user can manipulate the validation_rule parameter in the /api/form/upload endpoint to bypass file type restrictions. This vulnerability stems from insufficient server-side validation of the client-supplied validation_rule, which is directly passed to the Laravel validator. Successfully exploiting this vulnerability allows an attacker to upload arbitrary files, including PHP webshells, which can lead to remote code execution (RCE) if the storage disk is publicly accessible. The vulnerability was reported by zaurgsynv and has been patched in pull request #714. Defenders should ensure their Sharp instances are updated to version 9.20.0 or later, and restrict disk access.

Attack Chain

An authenticated user logs into the Sharp Laravel admin panel.
The user navigates to a section of the application that utilizes the file upload functionality.
The user intercepts the HTTP request sent to the /api/form/upload endpoint.
The user modifies the request body, specifically the validation_rule parameter, setting it to validation_rule[]=file.
The modified request is sent to the server, bypassing MIME type and file extension checks.
The server processes the upload request, saving the arbitrary file (e.g., a PHP webshell) to the designated storage disk.
If the storage disk is publicly accessible, the attacker can access the uploaded file via a web browser.
The attacker executes the uploaded PHP webshell, achieving remote code execution (RCE) on the server.

Impact

Successful exploitation of this vulnerability allows attackers to upload arbitrary files, including PHP webshells, to the affected server. This can lead to Remote Code Execution (RCE) if the server’s storage disk is misconfigured to be publicly accessible. While default configurations prevent direct execution of uploaded PHP files, compromised servers can be leveraged for lateral movement, data exfiltration, or further malicious activities. This vulnerability impacts all installations of code16/sharp prior to version 9.20.0.

Recommendation

Upgrade code16/sharp to version 9.20.0 or later to remediate CVE-2026-33687.
Ensure that the storage disk used for Sharp uploads is strictly private, as described in the Laravel filesystem documentation (https://laravel.com/docs/13.x/filesystem).
Deploy the Sigma rule “Detect Sharp File Upload Bypass Attempt” to identify attempts to exploit this vulnerability based on the validation_rule parameter.
Monitor web server logs for suspicious file uploads to the /api/form/upload endpoint, correlating with user activity and file extensions.