CVE-2009-1527 in Linux
Summary
by MITRE
Race condition in the ptrace_attach function in kernel/ptrace.c in the Linux kernel before 2.6.30-rc4 allows local users to gain privileges via a PTRACE_ATTACH ptrace call during an exec system call that is launching a setuid application, related to locking an incorrect cred_exec_mutex object.
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Analysis
by VulDB Data Team • 04/13/2025
The vulnerability described in CVE-2009-1527 represents a critical race condition within the Linux kernel's ptrace implementation that enables local privilege escalation attacks. This flaw exists in the ptrace_attach function located in kernel/ptrace.c and affects Linux kernel versions prior to 2.6.30-rc4. The vulnerability specifically exploits a timing window during which the kernel fails to properly acquire the correct locking mechanism when handling ptrace operations on setuid applications. The race condition occurs when a malicious local user attempts to attach to a process using PTRACE_ATTACH while that process is simultaneously executing an exec system call that launches a setuid application. This creates a temporal gap in the kernel's locking mechanism where the incorrect cred_exec_mutex object gets locked instead of the proper one, allowing attackers to manipulate the credential handling process.
The technical exploitation of this vulnerability involves a sophisticated understanding of kernel internals and process management mechanisms. When a process executes a setuid binary, the kernel must properly validate and transfer credentials to ensure the security boundaries are maintained. The race condition occurs because the ptrace subsystem does not properly synchronize access to the credential mutex during the critical phase of process execution. This improper locking allows an attacker to manipulate the credential structure before the proper validation occurs, potentially enabling the attacker to elevate privileges from a regular user to root level. The flaw is categorized under CWE-362, which specifically addresses Race Conditions, and aligns with ATT&CK technique T1068, which covers Exploitation for Privilege Escalation through local system vulnerabilities.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it represents a fundamental flaw in the kernel's security model that could be leveraged by malicious actors to gain unauthorized access to system resources. Attackers can exploit this vulnerability by carefully timing their ptrace operations to coincide with the execution of setuid binaries, effectively bypassing the kernel's privilege validation mechanisms. The vulnerability affects systems running Linux kernel versions before 2.6.30-rc4 and poses a significant risk to any system where local users might have the ability to execute processes or where setuid applications are present. Organizations using affected kernel versions face potential compromise of their entire system security posture, as the vulnerability allows attackers to bypass traditional access controls and escalate privileges without requiring additional attack vectors.
Mitigation strategies for CVE-2009-1527 primarily involve upgrading to a patched kernel version that addresses the race condition in the ptrace implementation. System administrators should immediately apply the appropriate kernel updates that include the fix for this vulnerability, which typically involves correcting the locking mechanism to ensure proper acquisition of the cred_exec_mutex object during process execution. Additionally, organizations should implement monitoring for suspicious ptrace activity and consider disabling unnecessary ptrace capabilities on systems where they are not required for legitimate system administration tasks. The vulnerability highlights the importance of proper kernel locking mechanisms and demonstrates how race conditions in critical system components can lead to severe security implications. Security teams should also review their system configurations to ensure that setuid applications are properly audited and that unnecessary privileges are not granted to local users. This vulnerability serves as a reminder of the critical importance of thorough testing and validation of kernel security patches before deployment in production environments.