CVE-2009-3612 in Linux
Summary
by MITRE
The tcf_fill_node function in net/sched/cls_api.c in the netlink subsystem in the Linux kernel 2.6.x before 2.6.32-rc5, and 2.4.37.6 and earlier, does not initialize a certain tcm__pad2 structure member, which might allow local users to obtain sensitive information from kernel memory via unspecified vectors. NOTE: this issue exists because of an incomplete fix for CVE-2005-4881.
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Analysis
by VulDB Data Team • 08/24/2021
The vulnerability described in CVE-2009-3612 represents a critical information disclosure flaw within the Linux kernel's netlink subsystem, specifically affecting the tcf_fill_node function in the net/sched/cls_api.c file. This issue manifests in kernel versions 2.6.x prior to 2.6.32-rc5 and 2.4.37.6 and earlier, where the tcm__pad2 structure member remains uninitialized during kernel memory operations. The flaw enables local attackers to potentially extract sensitive data from kernel memory spaces through unspecified vectors, creating a significant security risk for systems running affected kernel versions. The vulnerability's persistence stems from an incomplete remediation of a previously identified issue, CVE-2005-4881, which demonstrates the complexity of kernel security patches and the potential for residual vulnerabilities in system components.
The technical root cause of this vulnerability resides in the improper initialization of memory structures within the kernel's traffic control subsystem. When the tcf_fill_node function processes network classification data, it fails to properly initialize the tcm__pad2 member of the tc_message structure, leaving residual data from previous operations in memory. This uninitialized memory can contain sensitive information such as kernel pointers, security credentials, or other confidential data that was previously stored in those memory locations. The flaw operates at the kernel level where memory management and network packet processing intersect, making it particularly dangerous as it can be exploited by local users who have access to the system. The vulnerability aligns with CWE-457: Use of Uninitialized Variable, which specifically addresses the risks associated with uninitialized memory access in security-critical contexts.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially enable more sophisticated attacks when combined with other exploitation techniques. Local users who can execute code on the target system may leverage this flaw to gather kernel memory contents, which could reveal information about the kernel's internal state, memory layout, or security mechanisms. This information disclosure could aid attackers in developing more targeted exploits or bypassing security controls that depend on kernel memory integrity. The vulnerability's presence in both 2.4 and 2.6 kernel series indicates it affects a broad range of Linux systems, making it particularly concerning for organizations maintaining legacy systems or those that have not properly updated their kernel versions. From an attack perspective, this vulnerability maps to ATT&CK technique T1059.001: Command and Scripting Interpreter - PowerShell, as it provides attackers with additional information that can be used in subsequent attack phases.
The remediation for this vulnerability requires updating to kernel versions 2.6.32-rc5 or later, or 2.4.37.6 and later, where the uninitialized memory issue has been properly addressed. System administrators should prioritize kernel updates as part of their security maintenance procedures, particularly for systems running affected kernel versions. Additionally, organizations should implement monitoring to detect potential exploitation attempts and ensure that all systems are running patched kernel versions. The vulnerability's classification as a memory initialization error underscores the importance of thorough code review processes and comprehensive testing for security patches, as incomplete fixes can leave systems vulnerable to continued exploitation. Security teams should also consider implementing kernel hardening measures such as stack canaries, kernel address space layout randomization, and other mitigations to reduce the impact of similar vulnerabilities in the event they are not immediately patched.