CVE-1999-0778 in Accelerated-X Server
Summary
by MITRE
Buffer overflow in Xi Graphics Accelerated-X server allows local users to gain root access via a long display or query parameter.
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Analysis
by VulDB Data Team • 11/09/2024
The vulnerability identified as CVE-1999-0778 represents a critical buffer overflow flaw within the Xi Graphics Accelerated-X server implementation that enables local attackers to escalate their privileges to root access. This issue stems from inadequate input validation mechanisms within the X server's handling of display and query parameters, creating a pathway for malicious exploitation that can compromise system integrity and security posture.
The technical flaw manifests when the Accelerated-X server processes display or query parameters that exceed predetermined buffer size limitations. This buffer overflow occurs during the parsing of user-supplied input data, where the server fails to properly validate the length of incoming parameters before attempting to store them in fixed-size memory buffers. The vulnerability specifically affects the X server's handling of certain display name formats and query strings, allowing an attacker to overwrite adjacent memory locations including return addresses and control data structures. This type of flaw aligns with CWE-121, which categorizes buffer overflow conditions that occur when insufficient bounds checking is performed on buffers, and represents a classic example of stack-based buffer overflow exploitation techniques.
The operational impact of this vulnerability extends beyond simple privilege escalation as it fundamentally undermines the security model of the affected system. Local users who can execute code on the target system gain the ability to elevate their privileges to root level, effectively providing complete control over the compromised machine. This privilege escalation capability enables attackers to modify system files, install malicious software, create new user accounts, and access sensitive data that would otherwise remain protected. The vulnerability's local nature means that an attacker must already have access to the system through legitimate user accounts or other means, but once exploited, the consequences are severe enough to warrant immediate remediation. The attack vector involves crafting specifically formatted display names or query parameters that trigger the buffer overflow condition, typically through the use of specially crafted command line arguments or environment variables that are processed by the X server.
Mitigation strategies for CVE-1999-0778 require immediate attention through multiple layers of security controls. The primary remediation involves applying vendor-specific patches or updates that address the buffer overflow condition through proper input validation and bounds checking mechanisms. System administrators should implement the latest security updates from Xi Graphics or migrate to alternative X server implementations that have addressed this vulnerability. Additionally, privilege separation measures should be enforced to limit the execution scope of the X server process, reducing the potential impact of successful exploitation. Network segmentation and access controls can help limit local user access to systems running vulnerable X server implementations, while regular security audits should monitor for unauthorized modifications or attempts to exploit this vulnerability. The implementation of input validation controls and memory protection mechanisms such as stack canaries or address space layout randomization can provide additional defense in depth against similar buffer overflow exploits. Organizations should also consider implementing intrusion detection systems to monitor for suspicious parameter usage patterns that may indicate attempts to exploit this vulnerability, aligning with ATT&CK technique T1068 which covers local privilege escalation through system binary manipulation and exploitation of software vulnerabilities.