CVE-2007-6434 in Linux
Summary
by MITRE
Linux kernel 2.6.23 allows local users to create low pages in virtual userspace memory and bypass mmap_min_addr protection via a crafted executable file that calls the do_brk function.
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Analysis
by VulDB Data Team • 04/13/2019
The vulnerability identified as CVE-2007-6434 represents a significant security flaw in the Linux kernel version 2.6.23 that undermines critical memory protection mechanisms. This issue specifically targets the mmap_min_addr security feature, which was designed to prevent local privilege escalation by restricting the ability of user processes to map memory regions at very low virtual addresses. The vulnerability arises from improper validation within the kernel's memory management subsystem, particularly in how it handles the do_brk function during executable loading operations.
The technical exploitation of this vulnerability occurs when a local attacker crafts a specially designed executable file that deliberately invokes the do_brk function in a manner that circumvents the mmap_min_addr restrictions. This function is responsible for adjusting the break address of a process's heap, and the flaw allows attackers to create memory mappings at addresses below the minimum threshold that should normally be protected. The vulnerability essentially enables an attacker to bypass kernel-level memory protection controls that are fundamental to preventing certain types of privilege escalation attacks.
From an operational impact perspective, this vulnerability creates a serious threat to system security as it allows local users to potentially gain elevated privileges within the kernel space. The ability to manipulate virtual memory mappings at low addresses can be leveraged to bypass various security mitigations including those related to address space layout randomization and other kernel memory protection mechanisms. This vulnerability is particularly concerning because it operates at the kernel level and can be exploited by any user with local access to the system, potentially leading to complete system compromise.
The security implications of CVE-2007-6434 align with CWE-119, which addresses improper access to memory locations, and can be categorized under ATT&CK technique T1068, which involves local privilege escalation through kernel vulnerabilities. The vulnerability demonstrates a classic example of how kernel-level memory management flaws can be exploited to undermine fundamental security controls. Mitigation strategies should include applying the appropriate kernel security patches that address the memory management validation issues in the do_brk function. System administrators should also consider implementing additional security measures such as disabling unnecessary kernel features, monitoring for suspicious memory mapping activities, and ensuring that all systems are running patched kernel versions that have addressed this specific vulnerability. The vulnerability highlights the importance of maintaining up-to-date kernel security patches and demonstrates how seemingly minor memory management functions can have significant security implications when not properly validated against security constraints.