CVE-2022-31090 in Guzzle
Summary
by MITRE • 06/28/2022
Guzzle, an extensible PHP HTTP client. `Authorization` headers on requests are sensitive information. In affected versions when using our Curl handler, it is possible to use the `CURLOPT_HTTPAUTH` option to specify an `Authorization` header. On making a request which responds with a redirect to a URI with a different origin (change in host, scheme or port), if we choose to follow it, we should remove the `CURLOPT_HTTPAUTH` option before continuing, stopping curl from appending the `Authorization` header to the new request. Affected Guzzle 7 users should upgrade to Guzzle 7.4.5 as soon as possible. Affected users using any earlier series of Guzzle should upgrade to Guzzle 6.5.8 or 7.4.5. Note that a partial fix was implemented in Guzzle 7.4.2, where a change in host would trigger removal of the curl-added Authorization header, however this earlier fix did not cover change in scheme or change in port. If you do not require or expect redirects to be followed, one should simply disable redirects all together. Alternatively, one can specify to use the Guzzle steam handler backend, rather than curl.
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Analysis
by VulDB Data Team • 07/16/2022
The vulnerability described in CVE-2022-31090 represents a critical security flaw in the Guzzle HTTP client library for PHP, specifically affecting how authorization headers are handled during HTTP redirects. This issue stems from improper management of the CURLOPT_HTTPAUTH option when requests are redirected to different origins, creating potential exposure of sensitive authentication information. The vulnerability exists in the Curl handler implementation of Guzzle versions prior to 7.4.5, where the library fails to properly sanitize authentication headers when following redirects to URIs with different hostnames, schemes, or ports. This flaw directly relates to CWE-200, which addresses improper exposure of sensitive information, and CWE-306, concerning missing authentication. The vulnerability is particularly concerning because it could allow attackers to intercept and potentially exploit authentication credentials during legitimate HTTP redirect operations, which are common in web applications.
The technical implementation of this vulnerability occurs when Guzzle processes HTTP requests that result in redirects to different origins. During normal operation, when a request encounters a redirect response, the library should strip sensitive authorization headers before forwarding the request to the new location. However, in affected versions, the Curl handler maintains the CURLOPT_HTTPAUTH option across redirects, causing curl to automatically append the Authorization header to subsequent requests. This behavior is problematic because it violates the principle of least privilege and exposes authentication tokens to potentially unauthorized servers. The flaw is particularly severe when redirects occur to different ports or schemes, as these changes in origin are not properly handled by the partial fix implemented in version 7.4.2. The original implementation only addressed host changes but failed to account for scheme or port modifications, leaving applications vulnerable to credential leakage in these scenarios.
The operational impact of this vulnerability extends beyond simple information disclosure, as it could enable attackers to perform unauthorized actions on behalf of authenticated users. When an application using Guzzle makes a request that triggers a redirect to a malicious server, the authorization header could be automatically forwarded, potentially allowing unauthorized access to protected resources. This vulnerability affects both HTTP and HTTPS protocols, as well as different port configurations, making it particularly dangerous in environments where applications frequently interact with external services. The risk is amplified because redirect handling is a common pattern in web applications, particularly those using APIs, single sign-on systems, or content delivery networks. Organizations relying on affected Guzzle versions face potential data breaches, privilege escalation attacks, and unauthorized access to sensitive systems, with the severity of impact directly correlating to the sensitivity of the authentication tokens being exposed.
The recommended mitigation strategies for this vulnerability involve immediate version upgrades to the patched releases, specifically Guzzle 7.4.5 for version 7 users or 6.5.8 for version 6 users. This approach addresses the core issue by implementing comprehensive redirect handling that properly removes authentication options when following redirects to different origins. Additionally, organizations can disable redirects entirely if their applications do not require this functionality, which eliminates the attack surface entirely. Alternative approaches include switching to the Guzzle stream handler backend instead of the Curl handler, which does not exhibit the same vulnerability characteristics. Security teams should also conduct thorough audits of their applications to identify any usage of the affected Guzzle versions and implement proper monitoring for unauthorized redirect behaviors. The fix implemented in version 7.4.5 addresses the complete scope of the vulnerability by properly handling all types of origin changes including host, scheme, and port modifications, providing comprehensive protection against credential leakage during HTTP redirect operations. Organizations should also consider implementing additional security controls such as request/response monitoring, authentication token rotation, and network segmentation to further mitigate potential risks associated with this vulnerability.