CVE-2012-5630 in libuser
Summary
by MITRE
libuser 0.56 and 0.57 has a TOCTOU (time-of-check time-of-use) race condition when copying and removing directory trees.
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Analysis
by VulDB Data Team • 11/26/2019
The vulnerability identified as CVE-2012-5630 affects libuser versions 0.56 and 0.57, specifically targeting a time-of-check time-of-use race condition that occurs during directory tree operations. This flaw represents a classic concurrency issue where the system's behavior changes between the moment when a security check is performed and when the actual operation is executed. The vulnerability manifests when applications attempt to copy or remove directory trees, creating a window of opportunity for malicious actors to manipulate the filesystem state between these two phases. Such race conditions are particularly dangerous because they can be exploited to bypass security controls that rely on checking file or directory attributes before performing operations. The flaw exists within the core file system manipulation functions of libuser, which is a library commonly used for user and group management in unix-like operating systems, making it a critical component for system security.
The technical implementation of this TOCTOU vulnerability stems from the library's failure to maintain consistent state checks throughout the directory tree operations. When libuser performs copy or remove operations on directory trees, it first checks the permissions and attributes of directories and files, but does not lock or otherwise prevent concurrent modifications during the actual execution phase. This creates a temporal gap where an attacker can modify the directory structure, change file permissions, or even replace files with malicious content between the initial check and the final operation. The race condition is particularly problematic because it can be exploited to escalate privileges, bypass access controls, or perform unauthorized file system modifications. This vulnerability directly maps to CWE-367, which specifically addresses time-of-check to time-of-use race conditions, and represents a fundamental flaw in the library's design that fails to account for concurrent access patterns in multi-threaded or multi-process environments.
The operational impact of CVE-2012-5630 extends beyond simple privilege escalation, as it can enable attackers to gain unauthorized access to sensitive system resources and potentially compromise entire system integrity. Systems using affected versions of libuser are vulnerable to attacks that could allow unauthorized users to manipulate user accounts, modify system files, or bypass security controls designed to prevent such actions. The vulnerability affects the underlying file system operations that are fundamental to user management and system administration, making it particularly dangerous in multi-user environments where privilege separation is critical. Attackers can exploit this flaw to create malicious directory structures, replace critical system files, or manipulate user permissions in ways that could persist across system reboots. The impact is compounded by the fact that libuser is widely used across various unix-like systems, meaning that exploitation could affect a broad range of platforms and applications that depend on this library for user and group management operations.
Mitigation strategies for CVE-2012-5630 require immediate action to upgrade to patched versions of libuser, as the vulnerability cannot be effectively addressed through configuration changes or workarounds. Organizations should prioritize updating their systems to libuser versions that have addressed this race condition through proper locking mechanisms or atomic operations that prevent the temporal gap between checks and execution. The fix typically involves implementing proper synchronization mechanisms that ensure the state remains consistent throughout the entire directory tree operation process. Security teams should conduct comprehensive vulnerability assessments to identify all systems running affected libuser versions and establish remediation schedules that account for system downtime and testing requirements. Additionally, system administrators should monitor for exploitation attempts through log analysis and implement intrusion detection systems that can identify suspicious file system activities that might indicate exploitation of this vulnerability. The remediation process should also include verifying that all applications depending on libuser have been updated and tested to ensure compatibility with the patched versions.