CVE-2002-2092 in FreeBSD
Summary
by MITRE
Race condition in exec in OpenBSD 4.0 and earlier, NetBSD 1.5.2 and earlier, and FreeBSD 4.4 and earlier allows local users to gain privileges by attaching a debugger to a process before the kernel has determined that the process is setuid or setgid.
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Analysis
by VulDB Data Team • 09/06/2019
This vulnerability represents a critical race condition affecting multiple open source operating systems including OpenBSD 4.0 and earlier, NetBSD 1.5.2 and earlier, and FreeBSD 4.4 and earlier. The flaw occurs during the exec system call execution process when the kernel fails to properly synchronize the privilege checking mechanism with the debugger attachment process. This timing issue creates a window of opportunity where local attackers can exploit the system before the kernel has fully evaluated whether a process should be running with elevated privileges. The vulnerability specifically targets the sequence where a debugger attaches to a process that has not yet been fully processed by the kernel's privilege determination routines, allowing malicious code to potentially bypass security checks and escalate privileges.
The technical implementation of this race condition stems from the kernel's execution flow where the exec system call does not adequately prevent debugger attachment operations during the critical phase of process privilege evaluation. When a process is about to execute, the kernel must determine whether it should run with setuid or setgid permissions, but this determination occurs in a separate execution path that can be interrupted by debugger attachment operations. This creates an exploitable timing window where a malicious user can attach a debugger to the process before the kernel has made its final privilege decision. The vulnerability is classified under CWE-362, which specifically addresses race conditions in security-critical operations, and aligns with ATT&CK technique T1068 which covers privilege escalation through race conditions in system processes.
The operational impact of this vulnerability is severe as it allows local users to gain elevated privileges without requiring authentication or specialized knowledge of the system's internal workings. Attackers can leverage this flaw to execute arbitrary code with higher privileges than initially intended, potentially leading to complete system compromise. The vulnerability affects systems where debugging capabilities are available and where setuid/setgid binaries are commonly executed, making it particularly dangerous in multi-user environments or systems with debugging tools installed. The race condition is particularly problematic because it can be exploited without requiring network access or physical presence, and the exploitation can occur during normal system operation when processes are being executed.
Mitigation strategies for this vulnerability involve implementing proper kernel synchronization mechanisms to ensure that debugger attachment operations cannot occur during critical privilege evaluation phases. System administrators should immediately upgrade to patched versions of their operating systems, as this vulnerability was addressed in subsequent releases of all affected operating systems. The recommended approach includes applying security patches that modify the exec system call implementation to prevent race conditions between debugger attachment and privilege determination processes. Additionally, organizations should implement monitoring for unauthorized debugger attachment operations and consider disabling unnecessary debugging capabilities on production systems. The fix typically involves modifying the kernel's privilege checking code to ensure atomic execution of privilege evaluation and process attachment operations, preventing the timing window that enables exploitation. System hardening measures including disabling unnecessary debugging tools and restricting access to debugging capabilities can further reduce the attack surface for this particular vulnerability.