CVE-2015-9287 in mod_ucam_webauth
Summary
by MITRE
Directory Traversal was discovered in University of Cambridge mod_ucam_webauth before 2.0.2. The key identification field ("kid") of the IdP's HTTP response message ("WLS-Response") can be manipulated by an attacker. The "kid" field is not signed like the rest of the message, and manipulation is therefore trivial. The "kid" field should only ever represent an integer. However, it is possible to provide any string value. An attacker could use this to their advantage to force the application agent to load the RSA public key required for message integrity checking from an unintended location.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/15/2023
The vulnerability CVE-2015-9287 represents a critical directory traversal flaw in the University of Cambridge mod_ucam_webauth module prior to version 2.0.2, which operates as an Apache module for SAML-based authentication. This weakness stems from improper validation of the key identification field within the Identity Provider's HTTP response message known as "WLS-Response." The module's failure to properly sanitize the "kid" field creates a pathway for attackers to manipulate the cryptographic key loading process, potentially compromising the entire authentication infrastructure.
The technical exploitation of this vulnerability occurs through the manipulation of the "kid" field which is intended to contain only integer values representing key identifiers. However, the flawed implementation allows attackers to inject arbitrary string values into this field, bypassing the expected validation mechanisms. This manipulation enables adversaries to redirect the application agent to load RSA public keys from unintended file system locations, effectively undermining the message integrity checking mechanism that relies on proper key identification. The vulnerability is classified as a directory traversal issue under CWE-22, specifically manifesting as an improper input validation problem where the system fails to properly validate and sanitize user-supplied data before processing.
The operational impact of this vulnerability extends beyond simple authentication bypasses, as it fundamentally compromises the cryptographic security model of the SAML-based authentication system. Attackers can leverage this flaw to load malicious public keys from arbitrary locations, potentially enabling them to forge SAML responses or manipulate authentication decisions. The vulnerability creates a path for privilege escalation and unauthorized access to protected resources, as the system's ability to verify message integrity is completely undermined. This weakness directly aligns with ATT&CK technique T1552.001 for unsecured credentials and T1078.004 for valid accounts, as it enables attackers to manipulate the authentication process and potentially gain unauthorized access to systems.
Mitigation strategies for CVE-2015-9287 require immediate patching of the mod_ucam_webauth module to version 2.0.2 or later, which addresses the improper validation of the "kid" field. Organizations should implement strict input validation and sanitization measures for all fields within SAML response messages, particularly those used for cryptographic key identification. The fix should enforce that the "kid" field contains only integer values and reject any string-based inputs that could lead to directory traversal. Additionally, system administrators should review and restrict file system access permissions for cryptographic key files, implement proper logging and monitoring of authentication events, and ensure that all SAML implementations properly validate cryptographic signatures before processing authentication responses. The vulnerability demonstrates the critical importance of cryptographic key management and the necessity of proper input validation in security-critical systems, as highlighted in industry standards such as NIST SP 800-57 for key management and ISO/IEC 27001 for information security controls.