CVE-2018-6924 in FreeBSD
Summary
by MITRE
In FreeBSD before 11.1-STABLE, 11.2-RELEASE-p3, 11.1-RELEASE-p14, 10.4-STABLE, and 10.4-RELEASE-p12, insufficient validation in the ELF header parser could allow a malicious ELF binary to cause a kernel crash or disclose kernel memory.
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Analysis
by VulDB Data Team • 05/16/2023
The vulnerability identified as CVE-2018-6924 represents a critical flaw in the FreeBSD operating system's handling of executable and linkable format files. This issue affects multiple versions of FreeBSD including various stable and release branches, specifically targeting the kernel's ELF header parsing mechanism. The vulnerability stems from inadequate input validation within the kernel's ELF loader component, which processes executable files and shared libraries that are fundamental to system operation.
The technical nature of this vulnerability falls under CWE-125, which describes an out-of-bounds read condition where the kernel fails to properly validate the structure of ELF headers before processing them. When a maliciously crafted ELF binary is executed or loaded by the system, the insufficient validation allows an attacker to manipulate the parsing logic in such a way that it can either trigger a kernel panic leading to a system crash or potentially read sensitive kernel memory addresses. This occurs because the kernel's ELF parser does not adequately check the bounds of header fields or validate the integrity of the ELF structure before attempting to access specific memory locations.
The operational impact of this vulnerability extends beyond simple system instability as it creates potential attack vectors for privilege escalation and information disclosure. An attacker who can successfully exploit this vulnerability may gain access to kernel memory contents which could reveal sensitive information such as cryptographic keys, passwords, or other confidential data stored in kernel space. The vulnerability is particularly dangerous because it can be triggered through normal system operation when executing or loading malicious ELF files, making it difficult to prevent through traditional security measures. The affected versions span multiple release lines, indicating this was a widespread issue that required coordinated patches across different FreeBSD branches.
Mitigation strategies for this vulnerability involve applying the appropriate security patches released by the FreeBSD project, which typically include enhanced validation routines for ELF header parsing and bounds checking mechanisms. System administrators should prioritize updating their FreeBSD installations to versions 11.1-STABLE, 11.2-RELEASE-p3, 11.1-RELEASE-p14, 10.4-STABLE, and 10.4-RELEASE-p12 or later. Additionally, implementing proper file integrity monitoring and execution control measures can help detect and prevent exploitation attempts. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1059.007 for executing malicious code through compromised binaries, and T1068 for privilege escalation through kernel exploits. The vulnerability demonstrates the importance of robust input validation in kernel space operations and highlights the need for comprehensive security testing of system components that handle user-supplied data structures.