CVE-2009-0342 in Systrace
Summary
by MITRE
Niels Provos Systrace before 1.6f on the x86_64 Linux platform allows local users to bypass intended access restrictions by making a 64-bit syscall with a syscall number that corresponds to a policy-compliant 32-bit syscall.
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Analysis
by VulDB Data Team • 08/04/2021
The vulnerability described in CVE-2009-0342 represents a critical access control bypass issue within the Systrace system call filtering mechanism on x86_64 Linux platforms. This flaw specifically affects versions of Systrace prior to 1.6f and exploits a fundamental design oversight in how system call numbers are handled across different architectural contexts. The vulnerability stems from the improper handling of syscall numbers when transitioning from 32-bit to 64-bit system call interfaces, creating a pathway for local attackers to circumvent security policies that were intended to restrict system call execution.
The technical implementation of this vulnerability occurs through a specific syscall number mapping issue where a 64-bit system call with a particular number corresponds to a 32-bit syscall that is permitted by the current policy. This creates a discrepancy in the filtering mechanism that processes system calls based on their syscall numbers. When Systrace evaluates incoming system calls, it performs validation against its policy rules using the syscall numbers, but the 64-bit syscall interface does not properly account for the fact that certain syscall numbers may have different meanings or permissions when interpreted in 32-bit versus 64-bit contexts. The flaw allows attackers to leverage this mapping inconsistency to execute otherwise restricted system calls that are valid in 32-bit mode but would normally be blocked in 64-bit mode.
The operational impact of this vulnerability is significant for systems utilizing Systrace for security policy enforcement, particularly in environments where local privilege escalation is a concern. Local users can exploit this weakness to bypass access restrictions that were implemented to prevent execution of potentially dangerous system calls, effectively undermining the security posture of the system. The vulnerability is particularly concerning because it operates at the kernel level and can be exploited by any local user with access to the system, making it a persistent threat in multi-user environments. This type of bypass can enable attackers to perform actions such as file system modifications, process manipulation, or other privileged operations that should have been restricted by the security policy.
The vulnerability aligns with CWE-284, which addresses improper access control, and represents a classic case of insufficient privilege checking in system call filtering mechanisms. From an ATT&CK perspective, this vulnerability maps to technique T1068, which involves exploiting legitimate credentials and privileges to gain unauthorized access, and T1059, which covers command and scripting interpreter usage for persistence. The flaw demonstrates a fundamental weakness in the syscall filtering architecture that should be addressed through proper validation of system call numbers across different execution contexts. Organizations should implement immediate mitigation strategies including updating to Systrace version 1.6f or later, which contains the necessary patches to resolve the syscall number mapping issue. Additionally, system administrators should conduct thorough security audits to identify and remediate any other similar architectural inconsistencies in system call filtering mechanisms that could potentially create analogous vulnerabilities.