CVE-2002-1510 in X11r6
Summary
by MITRE
xdm, with the authComplain variable set to false, allows arbitrary attackers to connect to the X server if the xdm auth directory does not exist.
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability identified as CVE-2002-1510 resides within the X Display Manager xdm implementation where a critical security flaw exists in the authentication handling mechanism. This issue manifests when the authComplain variable is configured to false, creating a dangerous condition that fundamentally undermines the security posture of X Window System environments. The vulnerability specifically targets the absence of the xdm auth directory, which serves as a critical security control for managing authentication credentials and access permissions within X server environments.
The technical flaw operates through a privilege escalation mechanism where xdm fails to properly validate the existence of authentication directories when authComplain is disabled. This configuration allows unauthorized remote attackers to bypass normal authentication procedures and establish connections to the X server without proper credentials. The vulnerability stems from inadequate input validation and directory existence checking within the xdm authentication framework, creating an implicit trust relationship that should not exist. When the xdm auth directory does not exist, the system defaults to a permissive mode that accepts connections regardless of authentication status, effectively rendering the entire X server accessible to any remote attacker.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally compromises the integrity of the X Window System security model. Attackers can leverage this flaw to gain direct access to graphical user interfaces, potentially leading to session hijacking, privilege escalation, and further lateral movement within networked environments. The vulnerability affects systems where xdm is configured with authComplain=false and lacks proper authentication directory structures, making it particularly dangerous in multi-user environments where X server access is controlled. This weakness can enable attackers to execute malicious code through graphical interfaces, access sensitive user data, or establish persistent access points within target networks. The vulnerability aligns with CWE-284, which addresses improper access control in software systems, and represents a classic case of insecure default configurations that create security holes.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements to X server security. The primary fix involves ensuring that the xdm auth directory exists and is properly configured with appropriate permissions before xdm is started with authComplain=false. System administrators should verify that authentication directories are created with restrictive permissions and that proper ownership is maintained to prevent unauthorized modifications. Additionally, implementing proper access controls through xdm configuration files and ensuring that authComplain is set appropriately based on security requirements helps prevent exploitation. Organizations should also consider implementing network-level controls such as firewall rules that restrict access to X server ports, and regularly audit xdm configurations to ensure they align with security best practices. This vulnerability demonstrates the importance of proper security configuration management and highlights the critical need for robust authentication frameworks in graphical server environments, aligning with ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting through graphical interfaces.