CVE-2026-50157 in Symfony
Summary
by MITRE • 09/14/2026
Auth0 Symfony is a Symfony SDK for Auth0 Authentication and Management APIs. From 5.0.0-BETA0 until 5.9.0, the Authorizer::authenticate() and Authorizer::supports() paths in the Authorizer security authenticator may accept OAuth 2.0 bearer access tokens from the token URL query parameter as well as the Authorization header for protected HTTP routes. Query-string tokens can be recorded in server logs, browser history, or referrer data and then replayed against protected API endpoints. This issue is fixed in version 5.9.0.
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Analysis
by VulDB Data Team • 09/14/2026
The Auth0 Symfony SDK serves as a critical integration layer between applications built on the Symfony framework and the Auth0 identity management platform. Within versions ranging from 5.0.0-BETA0 through 5.9.0, a significant security flaw exists in the Authorizer component, specifically within the authenticate() and supports() methods of the security authenticator. This vulnerability stems from an overly permissive token parsing mechanism that fails to strictly enforce standard HTTP authentication protocols for protected routes. Instead of exclusively accepting OAuth 2.0 bearer access tokens via the Authorization header, as mandated by RFC 6750, the implementation also accepts these sensitive credentials when passed in the query string parameter named token. This deviation from industry best practices introduces severe risks regarding credential exposure and subsequent unauthorized access.
The core technical flaw lies in the lack of strict input validation regarding the location of authentication tokens. By allowing bearer tokens to be transmitted via URL parameters, the application inadvertently exposes these secrets to multiple vectors where they are typically logged or cached. Web servers routinely log full request URLs for diagnostic and analytics purposes, meaning any token passed as a query parameter will likely appear in plain text within access logs. Furthermore, modern web browsers often record visited URLs in history, and HTTP referrer headers may transmit the URL containing the token to third-party domains if links are followed from protected pages. This behavior creates a persistent state where sensitive authentication material is stored in multiple insecure locations outside of application control.
The operational impact of this vulnerability is substantial, primarily facilitating credential replay attacks. An attacker who gains access to server logs, browser history, or referrer data can extract the bearer token and reuse it to authenticate against protected API endpoints without needing further credentials such as a password or multi-factor authentication code. This effectively bypasses the intended security controls, allowing unauthorized entities to impersonate legitimate users. The risk is exacerbated in environments where log files are accessible to multiple administrators or stored in centralized logging systems with varying levels of access control. Additionally, if the application operates over unencrypted HTTP connections, these tokens would be exposed on the network wire as well, although even over HTTPS, the storage and transmission via referrers remain critical risks.
This vulnerability aligns closely with CWE-598: Use of GET Request Method To Retrieve Sensitive Data, which highlights the dangers of placing sensitive information in URLs that are logged or cached. It also relates to CWE-200: Exposure of Sensitive Information to an Unauthorized Actor, as the token becomes visible to unintended parties through logs and browser artifacts. From a threat modeling perspective using MITRE ATT&CK techniques, this flaw facilitates T1539: Steal Web Session Cookie, although in this case it applies specifically to bearer tokens rather than session cookies. The attack vector is classified under T1078: Valid Accounts if the attacker replays stolen credentials, and potentially T1114: Email Collection or T1123: Audio Capture depending on how the logs are exfiltrated by an insider threat or compromised system.
To mitigate this vulnerability, organizations must immediately upgrade to Auth0 Symfony SDK version 5.9.0 or later, where the Authorizer has been patched to reject tokens passed via query parameters and enforce strict adherence to the Authorization header for authentication. For applications that cannot be upgraded instantly due to dependency constraints, a temporary mitigation involves implementing custom middleware or event listeners within the Symfony application to explicitly strip or reject any request containing an authorization token in the URL query string before it reaches the Auth0 authenticator. Additionally, administrators should review server access logs and browser history policies to ensure that sensitive data is not being inadvertently persisted. Implementing strict Content Security Policy headers can also help mitigate referrer-based leakage by controlling how much information is sent with requests to other origins. Regular security audits of authentication flows are recommended to prevent similar deviations from OAuth 2.0 standards in the future.