CVE-2010-3690 in phpCAS
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in phpCAS before 1.1.3, when proxy mode is enabled, allow remote attackers to inject arbitrary web script or HTML via (1) a crafted Proxy Granting Ticket IOU (PGTiou) parameter to the callback function in client.php, (2) vectors involving functions that make getCallbackURL calls, or (3) vectors involving functions that make getURL calls.
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Analysis
by VulDB Data Team • 09/26/2021
The vulnerability identified as CVE-2010-3690 represents a critical cross-site scripting flaw in the phpCAS library version 1.1.2 and earlier, specifically when operating in proxy mode. This vulnerability exposes applications that utilize phpCAS for single sign-on authentication to potential malicious injection attacks that could compromise user sessions and data integrity. The flaw exists within the library's handling of proxy-related parameters and URL construction functions, creating attack vectors that allow remote adversaries to execute arbitrary web scripts in the context of authenticated users' browsers.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the phpCAS library's proxy mode functionality. Attackers can exploit three distinct vectors to inject malicious content through the PGTiou parameter in the callback function within client.php, as well as through functions that generate callback URLs and direct URL calls. The vulnerability specifically affects applications that enable proxy mode in phpCAS, where the library acts as a proxy between the user and the service provider, creating additional attack surface areas for malicious actors. The flaw manifests when the library fails to properly sanitize user-supplied parameters before incorporating them into web responses, allowing attackers to inject script code that executes in the victim's browser context.
The operational impact of this vulnerability is significant for organizations relying on phpCAS for authentication services, particularly those operating in environments where proxy mode is enabled. An attacker who successfully exploits this vulnerability could execute malicious scripts in the context of authenticated users, potentially leading to session hijacking, credential theft, or unauthorized access to protected resources. The attack requires minimal privileges and can be executed remotely, making it particularly dangerous for web applications that depend on phpCAS for secure authentication. The vulnerability affects any application using phpCAS version 1.1.2 or earlier in proxy mode, creating widespread potential exposure across numerous web applications that implement this authentication library.
Organizations should immediately upgrade to phpCAS version 1.1.3 or later, which includes proper input validation and output encoding fixes for the affected parameters. Additionally, implementing proper input sanitization at the application level, using content security policies, and monitoring for suspicious parameter values can provide additional defense layers. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and represents a typical example of how insecure parameter handling in authentication libraries can create persistent security risks. From an attack perspective, this vulnerability maps to ATT&CK technique T1566, specifically the use of malicious web content to exploit authentication systems, making it a critical concern for organizations implementing single sign-on solutions.