CVE-2009-0835 in Linux
Summary
by MITRE
The __secure_computing function in kernel/seccomp.c in the seccomp subsystem in the Linux kernel 2.6.28.7 and earlier on the x86_64 platform, when CONFIG_SECCOMP is enabled, does not properly handle (1) a 32-bit process making a 64-bit syscall or (2) a 64-bit process making a 32-bit syscall, which allows local users to bypass intended access restrictions via crafted syscalls that are misinterpreted as (a) stat or (b) chmod, a related issue to CVE-2009-0342 and CVE-2009-0343.
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Analysis
by VulDB Data Team • 12/20/2024
The vulnerability described in CVE-2009-0835 resides within the Linux kernel's seccomp subsystem, specifically in the __secure_computing function located in kernel/seccomp.c. This flaw affects Linux kernel versions 2.6.28.7 and earlier, particularly on x86_64 platforms where CONFIG_SECCOMP is enabled. The issue stems from improper handling of syscall architecture transitions, creating a critical bypass mechanism for local attackers seeking to circumvent security restrictions. The vulnerability manifests when processes attempt to make syscalls across different architectures, specifically when 32-bit processes invoke 64-bit syscalls or vice versa, allowing malicious code to exploit architectural mismatch conditions for privilege escalation.
The technical implementation of this vulnerability exploits a fundamental flaw in syscall validation within the seccomp framework. When a process makes a syscall that crosses architecture boundaries, the __secure_computing function fails to properly validate the syscall parameters, leading to misinterpretation of the intended syscall. Attackers can craft specific syscalls that appear to be benign operations like stat or chmod but are actually designed to trigger the architectural mismatch condition. This misinterpretation allows the system to bypass intended access controls and execute unauthorized operations. The vulnerability directly relates to CWE-191, which addresses integer underflow conditions, and represents a classic case of improper input validation in kernel space. The flaw essentially creates a pathway where syscall validation logic fails to properly account for architecture-specific syscall numbers and their corresponding parameter handling.
The operational impact of this vulnerability is significant for systems running affected kernel versions, as it provides local users with a means to bypass security controls that are specifically designed to restrict system access. The vulnerability is particularly dangerous because it operates at the kernel level, where successful exploitation can lead to complete system compromise. Attackers can leverage this weakness to escalate privileges, execute arbitrary code, or bypass mandatory access controls that are typically enforced by the seccomp framework. The relationship to CVE-2009-0342 and CVE-2009-0343 demonstrates that this issue is part of a broader class of architecture transition vulnerabilities that affect the Linux kernel's security model. From an ATT&CK perspective, this vulnerability maps to privilege escalation techniques and can be categorized under T1068, which involves exploiting vulnerabilities in the operating system to gain elevated privileges.
Mitigation strategies for CVE-2009-0835 primarily focus on kernel updates and system hardening measures. The most effective solution involves upgrading to a patched kernel version that addresses the architectural mismatch handling in the seccomp subsystem. System administrators should also implement additional security controls such as disabling unnecessary syscalls, configuring more restrictive seccomp profiles, and monitoring for unusual syscall patterns that might indicate exploitation attempts. Organizations should consider implementing runtime protections and anomaly detection systems to identify potential exploitation attempts. The vulnerability highlights the importance of proper syscall validation across architecture boundaries and underscores the need for comprehensive testing of security mechanisms when dealing with mixed-architecture environments. Additionally, implementing proper privilege separation and reducing the attack surface through careful syscall filtering can help minimize the impact of such vulnerabilities in environments where kernel updates cannot be immediately deployed.