CVE-2003-0987 in HTTP Server
Summary
by MITRE
mod_digest for Apache before 1.3.31 does not properly verify the nonce of a client response by using a AuthNonce secret.
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Analysis
by VulDB Data Team • 05/23/2019
The vulnerability described in CVE-2003-0987 affects the mod_digest module in Apache HTTP Server versions prior to 1.3.31, representing a critical authentication weakness that undermines the security of digest authentication mechanisms. This flaw resides in the module's implementation of nonce validation, which is a fundamental component of the HTTP digest authentication protocol designed to prevent replay attacks and ensure the integrity of client authentication responses.
The technical flaw stems from the improper verification of the AuthNonce secret within the digest authentication process. In properly functioning digest authentication, the server generates a unique nonce value for each authentication request, which the client incorporates into its response hash. The server must then validate this nonce to ensure it has not been tampered with or replayed. However, in affected Apache versions, the mod_digest module fails to adequately verify the nonce by relying on an insufficiently secure secret mechanism that allows attackers to bypass the authentication checks.
This vulnerability creates significant operational impact by enabling several attack vectors that can compromise the confidentiality and integrity of protected resources. An attacker can exploit this weakness to perform unauthorized access to web applications that rely on digest authentication, potentially gaining access to sensitive data, administrative functions, or system resources. The attack requires minimal privileges and can be executed against any web application using the vulnerable mod_digest module, making it particularly dangerous in environments where digest authentication is deployed.
The vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in authentication mechanisms, specifically focusing on the improper implementation of cryptographic functions. From an ATT&CK perspective, this weakness maps to T1110.002, which covers credential access through brute force or cryptographic attacks, and T1566, which involves the exploitation of vulnerabilities in web applications. The attack chain typically involves capturing authentication requests, extracting the nonce value, and then crafting modified responses that bypass the authentication validation process.
Mitigation strategies for this vulnerability center on immediate patching of the Apache HTTP Server to version 1.3.31 or later, which contains the corrected nonce validation implementation. Organizations should also consider implementing additional security controls such as enforcing the use of stronger authentication mechanisms like HTTP Basic authentication with TLS encryption, or transitioning to more secure alternatives such as OAuth or SAML-based authentication. Network segmentation and monitoring of authentication attempts can provide additional layers of defense. Regular security audits of web server configurations and authentication mechanisms should be conducted to identify and remediate similar vulnerabilities in other components of the infrastructure.