CVE-2008-5029 in Linux
Summary
by MITRE
The __scm_destroy function in net/core/scm.c in the Linux kernel 2.6.27.4, 2.6.26, and earlier makes indirect recursive calls to itself through calls to the fput function, which allows local users to cause a denial of service (panic) via vectors related to sending an SCM_RIGHTS message through a UNIX domain socket and closing file descriptors.
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Analysis
by VulDB Data Team • 08/21/2019
The vulnerability described in CVE-2008-5029 represents a critical recursive call issue within the Linux kernel's socket communication subsystem. This flaw exists in the __scm_destroy function located in net/core/scm.c, affecting kernel versions 2.6.27.4 and earlier, as well as 2.6.26 and prior releases. The vulnerability stems from improper handling of file descriptor cleanup during SCM_RIGHTS message transmission through UNIX domain sockets, creating a dangerous recursive call pattern that can lead to system instability.
The technical implementation of this vulnerability involves indirect recursive calls that occur when the __scm_destroy function invokes the fput function, which in turn triggers additional calls back to __scm_destroy. This creates a call stack that can grow indefinitely until system resources are exhausted, resulting in kernel panic and system crash. The recursive nature of this flaw means that each file descriptor closure operation can potentially trigger multiple additional cleanup operations, exponentially increasing the call depth and system resource consumption.
The operational impact of CVE-2008-5029 is severe as it allows local users to deliberately trigger a denial of service condition that can bring entire systems down. Attackers need only send an SCM_RIGHTS message through a UNIX domain socket and then close the associated file descriptors to initiate the recursive call chain. This vulnerability is particularly dangerous because it requires minimal privileges and can be exploited by any local user with access to UNIX domain sockets, making it a significant threat to system availability and stability. The vulnerability aligns with CWE-674, which describes "Uncontrolled Recursion" in software systems.
This flaw demonstrates a fundamental issue in kernel memory management and resource cleanup procedures, particularly concerning how file descriptor references are handled during socket communication. The vulnerability operates at the kernel level and leverages the standard UNIX domain socket interface, making it difficult to detect and prevent through conventional application-level security measures. The exploitability of this vulnerability is enhanced by the fact that it can be triggered through normal system operations, making it challenging to distinguish between legitimate and malicious usage patterns.
The mitigation strategies for CVE-2008-5029 primarily involve upgrading to kernel versions that contain the appropriate patches, specifically those released after the vulnerability was identified. System administrators should prioritize applying these kernel updates to prevent exploitation, as the vulnerability cannot be effectively mitigated through configuration changes or access controls. Additionally, monitoring for unusual patterns of socket communication and file descriptor operations can help detect potential exploitation attempts, though this approach is not foolproof given the nature of the vulnerability.
From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to "Virtualization/Sandbox Evasion" and the T1059.001 technique for "Command and Scripting Interpreter" through local privilege escalation. The vulnerability represents a critical weakness in the kernel's resource management capabilities that can be exploited to achieve system-level compromise. Organizations should implement comprehensive kernel patch management procedures and maintain up-to-date security monitoring to protect against this and similar vulnerabilities that could be used as initial access vectors for more sophisticated attacks.