CVE-2008-2148 in Linux
Summary
by MITRE
The utimensat system call (sys_utimensat) in Linux kernel 2.6.22 and other versions before 2.6.25.3 does not check file permissions when certain UTIME_NOW and UTIME_OMIT combinations are used, which allows local users to modify file times of arbitrary files, possibly leading to a denial of service.
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Analysis
by VulDB Data Team • 08/12/2019
The vulnerability identified as CVE-2008-2148 represents a critical permission bypass flaw within the Linux kernel's implementation of the utimensat system call. This system call serves the essential function of setting file access and modification times, operating through the sys_utimensat kernel interface that handles time-related metadata updates for files and directories. The vulnerability specifically manifests in kernel versions prior to 2.6.25.3, where the implementation fails to properly validate file permissions during certain combinations of UTIME_NOW and UTIME_OMIT constants. This design oversight creates a scenario where local attackers can manipulate file timestamps without proper authorization, effectively circumventing the standard file permission mechanisms that should normally restrict such operations.
The technical exploitation of this vulnerability relies on the specific interaction between the utimensat system call and its parameter handling when processing time modification requests. When attackers pass combinations of UTIME_NOW and UTIME_OMIT constants to the system call, the kernel's permission checking logic becomes bypassed, allowing arbitrary file time modifications regardless of the target file's access permissions. This flaw operates at the kernel level and requires local system access, making it a local privilege escalation vulnerability that can be exploited by users with minimal system privileges. The vulnerability is classified under CWE-264, which addresses permissions, privileges, and access control issues in software systems, specifically targeting the failure to properly enforce access controls during system calls. The underlying mechanism exploits the kernel's insufficient validation of file access rights when processing time modification requests, creating a pathway for unauthorized timestamp alterations.
The operational impact of CVE-2008-2148 extends beyond simple timestamp manipulation, potentially enabling more sophisticated attacks that can disrupt system integrity and availability. Local users who exploit this vulnerability can modify timestamps on critical system files, which may interfere with backup systems, log analysis, and security monitoring tools that rely on accurate file metadata. The ability to manipulate file times can also be leveraged to evade detection mechanisms, as security tools often monitor for suspicious timestamp changes that might indicate malicious activity. This vulnerability can contribute to denial of service conditions when the manipulated file times cause cascading failures in applications that depend on proper file metadata for their operation. Additionally, the flaw can be combined with other techniques to create more complex attack scenarios, making it particularly dangerous in environments where multiple security controls are in place. The ATT&CK framework categorizes this as a privilege escalation technique under the T1068 category, which involves the exploitation of system vulnerabilities to gain elevated privileges, and specifically relates to the use of system call vulnerabilities for unauthorized access.
Mitigation strategies for CVE-2008-2148 primarily focus on kernel version upgrades and system hardening measures. System administrators should immediately upgrade to Linux kernel versions 2.6.25.3 or later, where the vulnerability has been patched through proper permission validation in the utimensat implementation. The patch addresses the core issue by ensuring that file access permissions are consistently checked regardless of the UTIME_NOW and UTIME_OMIT parameter combinations used in system calls. Organizations should implement comprehensive system monitoring to detect unauthorized timestamp modifications, particularly focusing on critical system files and security-related artifacts. Regular security audits should verify that file permissions are properly enforced and that no unauthorized modifications have occurred. Additional defensive measures include implementing proper system access controls, monitoring for unusual system call patterns, and maintaining up-to-date security patches across all system components. The vulnerability demonstrates the critical importance of proper permission validation in kernel-level system calls and highlights the need for thorough security testing of core operating system functions. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain comprehensive incident response procedures for detecting and responding to potential exploitation attempts.