CVE-2009-2697 in GDM
Summary
by MITRE
The Red Hat build script for the GNOME Display Manager (GDM) before 2.16.0-56 on Red Hat Enterprise Linux (RHEL) 5 omits TCP Wrapper support, which might allow remote attackers to bypass intended access restrictions via XDMCP connections, a different vulnerability than CVE-2007-5079.
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Analysis
by VulDB Data Team • 03/30/2025
The vulnerability described in CVE-2009-2697 pertains to a critical security flaw in the GNOME Display Manager (GDM) build configuration on Red Hat Enterprise Linux 5 systems. This issue specifically affects the build script used by Red Hat to package GDM, where TCP Wrapper support was inadvertently omitted during the compilation process. The omission creates a significant security gap that directly impacts the system's ability to enforce access controls for XDMCP (X Display Manager Control Protocol) connections, which are essential for remote display management and authentication within Unix-like operating systems.
The technical flaw manifests in the build configuration process where the TCP Wrapper library support was not properly included in the GDM package compilation. TCP Wrappers provide a robust access control mechanism that allows system administrators to specify which hosts can connect to network services through the /etc/hosts.allow and /etc/hosts.deny configuration files. When this support is missing from GDM, the display manager cannot properly enforce the access restrictions that would normally prevent unauthorized remote connections to the X server. This creates an attack vector where remote adversaries can bypass intended access controls and establish XDMCP connections without proper authentication, potentially leading to unauthorized access to graphical user interfaces and underlying system resources.
The operational impact of this vulnerability extends beyond simple access control bypass, as it fundamentally undermines the security posture of systems running affected versions of GDM. XDMCP connections are commonly used for remote desktop access and display management, making this vulnerability particularly dangerous in enterprise environments where graphical access to systems is required. Attackers could exploit this weakness to gain unauthorized access to user sessions, potentially leading to privilege escalation, data theft, or further network infiltration. The vulnerability operates at the network level, allowing attackers to connect to the X server without proper authentication, which could be leveraged as a stepping stone for more sophisticated attacks within the network infrastructure.
This security gap represents a configuration management failure that aligns with CWE-1004 weakness category, specifically related to insecure default settings and missing security controls in software builds. The vulnerability also maps to ATT&CK technique T1078.001 which covers valid accounts and T1021.001 which covers remote services, as it enables unauthorized access to legitimate remote services through compromised authentication mechanisms. Organizations running affected RHEL 5 systems are particularly vulnerable as they lack the proper network access controls that TCP Wrappers would normally provide, creating an environment where attackers can bypass security measures that should prevent unauthorized XDMCP connections. The absence of this security feature makes systems more susceptible to reconnaissance and exploitation activities targeting display management services.
The recommended mitigation strategy involves upgrading to GDM version 2.16.0-56 or later, which properly includes TCP Wrapper support in the build configuration. System administrators should also implement additional network-level controls such as firewall rules to restrict access to XDMCP ports, typically TCP port 177, and ensure that only trusted hosts can connect to these services. Network segmentation and monitoring of XDMCP connections can provide additional layers of defense. Organizations should also review their access control policies and ensure that unnecessary XDMCP services are disabled or properly restricted to prevent exploitation of this vulnerability. Regular security audits of build configurations and software packages are essential to prevent similar issues from occurring in other system components.