CVE-2003-0690 in KDE
Summary
by MITRE
KDM in KDE 3.1.3 and earlier does not verify whether the pam_setcred function call succeeds, which may allow attackers to gain root privileges by triggering error conditions within PAM modules, as demonstrated in certain configurations of the MIT pam_krb5 module.
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Analysis
by VulDB Data Team • 05/29/2019
The vulnerability identified as CVE-2003-0690 represents a critical authentication flaw within the KDE Display Manager KDM version 3.1.3 and earlier implementations. This issue specifically targets the handling of PAM (Pluggable Authentication Modules) credential management functions during the authentication process. The flaw occurs when KDM fails to properly validate the success of pam_setcred function calls, creating a potential privilege escalation vector that could be exploited by malicious actors.
The technical root cause of this vulnerability lies in the improper error handling within KDM's integration with PAM subsystems. When PAM modules are invoked during authentication, the pam_setcred function is responsible for setting up user credentials and establishing the appropriate security context. In affected KDE versions, KDM does not check whether this function completes successfully, allowing the authentication process to proceed even when credential setup fails. This oversight creates a scenario where attackers can manipulate PAM modules to trigger specific error conditions that should normally prevent authentication from succeeding.
The operational impact of this vulnerability is particularly severe as it can potentially allow local attackers to escalate privileges to the root level. The exploitation mechanism specifically leverages configurations where the MIT pam_krb5 module is in use, demonstrating how certain PAM module implementations can be manipulated to bypass authentication controls. When the pam_setcred function fails in specific configurations, the authentication process continues without proper credential validation, creating a window for unauthorized privilege elevation. This vulnerability affects systems running KDE 3.1.3 or earlier versions where KDM serves as the display manager.
This vulnerability maps directly to CWE-284, which addresses improper access control in authentication systems, and aligns with ATT&CK technique T1068, which covers privilege escalation through local exploitation. The flaw demonstrates poor input validation and error handling practices that violate fundamental security principles for authentication systems. Organizations using affected KDE versions should immediately apply patches or upgrade to newer releases that properly validate PAM function return codes and implement robust error handling mechanisms.
The security implications extend beyond simple privilege escalation as this vulnerability could enable attackers to gain complete system control. Proper implementation of PAM credential verification should include checking return codes from pam_setcred and other critical PAM functions to ensure authentication integrity. This vulnerability highlights the importance of comprehensive error handling in security-critical components and underscores the need for regular security audits of authentication subsystems. Systems administrators should also consider implementing additional monitoring and logging of authentication events to detect potential exploitation attempts. The fix for this vulnerability required modifications to KDM's PAM integration code to properly validate function return values and implement appropriate error recovery mechanisms.
This vulnerability serves as a classic example of how seemingly minor implementation flaws in authentication systems can lead to significant security consequences. The issue demonstrates the critical importance of thorough testing of authentication flows and proper error handling in security-sensitive applications. Organizations should ensure that all authentication components properly validate function return codes and implement comprehensive error recovery procedures to prevent similar vulnerabilities from occurring in other systems. The remediation process involves updating to patched versions of KDE that properly handle PAM credential verification and implementing proper security controls to prevent unauthorized privilege escalation attempts.