CVE-2005-0108 in mod_auth_radius
Summary
by MITRE
Apache mod_auth_radius 1.5.4 and libpam-radius-auth allow remote malicious RADIUS servers to cause a denial of service (crash) via a RADIUS_REPLY_MESSAGE with a RADIUS attribute length of 1, which leads to a memcpy operation with a -1 length argument.
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Analysis
by VulDB Data Team • 05/29/2019
The vulnerability described in CVE-2005-0108 represents a critical denial of service flaw affecting Apache mod_auth_radius 1.5.4 and libpam-radius-auth authentication modules. This issue arises from inadequate input validation within the RADIUS protocol implementation, specifically when processing authentication responses from remote RADIUS servers. The flaw manifests when a malicious RADIUS server sends a RADIUS_REPLY_MESSAGE containing an attribute with a length field set to 1, which subsequently triggers a malformed memory operation within the affected software components.
The technical root cause of this vulnerability stems from improper bounds checking and integer handling within the RADIUS attribute parsing logic. When the authentication module encounters a RADIUS attribute with an invalid length of 1, the processing routine attempts to execute a memcpy operation with a negative length argument, specifically -1. This occurs due to integer underflow conditions where the length value is interpreted as a signed integer and subsequently converted to an unsigned value, resulting in a massive negative value that corrupts memory management operations. The vulnerability is classified under CWE-129 as an improper validation of length parameter, while also demonstrating characteristics of CWE-191 related to integer underflow conditions.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides malicious actors with a straightforward method to crash authentication services without requiring authentication credentials or complex exploitation techniques. When exploited, the vulnerability causes the affected Apache modules or PAM authentication framework to crash, resulting in complete denial of service for legitimate authentication requests. This affects systems relying on RADIUS authentication for network access control, VPN services, wireless authentication, and other network security infrastructures that depend on the mod_auth_radius or libpam-radius-auth components.
Systems utilizing RADIUS authentication are particularly vulnerable since the attack can be executed remotely without requiring physical access or elevated privileges. The vulnerability affects both web servers using mod_auth_radius for authentication and Unix/Linux systems using libpam-radius-auth for PAM-based authentication. Network administrators should note that the attack vector is extremely low-risk for the attacker, requiring only the ability to control or compromise a RADIUS server, which could be achieved through various means including network interception, compromised third-party services, or insider threats. The vulnerability also aligns with ATT&CK technique T1566 related to credential access through network infrastructure manipulation.
Mitigation strategies should focus on immediate patching of affected software versions, with the recommended approach being the upgrade to patched versions of mod_auth_radius and libpam-radius-auth. Organizations should also implement network segmentation to isolate RADIUS servers and employ network monitoring to detect unusual RADIUS traffic patterns. Additional defensive measures include configuring firewalls to restrict RADIUS server access to trusted networks only, implementing RADIUS server authentication mechanisms such as shared secrets, and deploying intrusion detection systems to monitor for malformed RADIUS attribute lengths. The vulnerability demonstrates the importance of robust input validation in network protocol implementations and highlights the need for comprehensive security testing of authentication infrastructure components.