CVE-1999-0965 in Xterm
Summary
by MITRE
race condition in xterm allows local users to modify arbitrary files via the logging option.
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Analysis
by VulDB Data Team • 11/19/2024
The vulnerability identified as CVE-1999-0965 represents a critical race condition flaw within the xterm terminal emulator that was prevalent in Unix-like operating systems during the late 1990s. This security weakness specifically manifests when the xterm application utilizes its logging functionality, creating a window of opportunity for malicious local users to exploit temporal inconsistencies in file access controls. The race condition occurs during the process of file creation and access validation, where the application's timing-dependent operations can be manipulated by adversaries to gain unauthorized access to system resources.
The technical implementation of this vulnerability stems from the improper handling of file permissions and access checks within xterm's logging mechanism. When a user enables logging functionality, the application creates log files in a manner that does not adequately synchronize file creation with permission verification. This temporal gap allows a local attacker to perform a race condition attack by creating symbolic links or manipulating file paths between the time when permission checks occur and when the actual file operations are executed. The flaw is categorized under CWE-367, which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) vulnerabilities, where the state of a resource changes between the time it is checked and the time it is used.
From an operational perspective, this vulnerability poses significant risks to system security as it enables local users to potentially modify files that they would normally not have access to. The attack vector requires local system access but does not necessitate elevated privileges, making it particularly dangerous in multi-user environments where users might share system resources. An attacker could leverage this weakness to overwrite critical system files, inject malicious content into log files, or modify configuration settings that could compromise system integrity and availability. The impact extends beyond simple file modification as it can potentially facilitate privilege escalation or persistent access mechanisms within the compromised system.
The mitigation strategies for CVE-1999-0965 primarily involve immediate software updates and system hardening measures. System administrators should ensure that all xterm installations are updated to versions that properly address the race condition through synchronized file access operations and proper file creation atomicity. Additionally, implementing proper file system permissions and using secure coding practices that prevent TOCTOU vulnerabilities should be enforced across all terminal applications. The remediation process should include disabling unnecessary logging features when not required and implementing monitoring solutions to detect anomalous file access patterns that might indicate exploitation attempts. Organizations should also consider implementing the principle of least privilege and regularly auditing system configurations to minimize the potential impact of such vulnerabilities. This issue aligns with ATT&CK technique T1059.007 for terminal shell access and T1078 for valid accounts, as it exploits legitimate system access to perform unauthorized file modifications.