CVE-2006-4178 in FreeBSD
Summary
by MITRE
Integer signedness error in the i386_set_ldt call in FreeBSD 5.5, and possibly earlier versions down to 5.2, allows local users to cause a denial of service (crash) via unspecified arguments that use negative signed integers to cause the bzero function to be called with a large length parameter, a different vulnerability than CVE-2006-4172.
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Analysis
by VulDB Data Team • 01/01/2025
The vulnerability described in CVE-2006-4178 represents a critical integer signedness error within the FreeBSD operating system kernel, specifically affecting versions 5.5 and potentially earlier versions down to 5.2. This flaw exists within the i386_set_ldt system call implementation, which is responsible for managing the Local Descriptor Table in x86 architecture systems. The issue arises from improper handling of integer parameters that are expected to be unsigned but are processed as signed integers, creating a dangerous condition where negative values can be interpreted as extremely large positive numbers.
The technical exploitation of this vulnerability occurs when local users provide unspecified arguments to the i386_set_ldt system call that contain negative signed integers. When these values are passed through the kernel's internal processing logic, they eventually reach the bzero function which is designed to zero out memory regions. Due to the signedness error, negative integers are interpreted as massive unsigned values, causing the bzero function to attempt to clear an enormous memory region that far exceeds the actual available memory space. This results in kernel memory corruption and ultimately leads to system crashes or denial of service conditions that can bring the entire operating system to a halt.
This vulnerability demonstrates characteristics consistent with CWE-190, Integer Overflow or Wraparound, where the improper handling of integer values leads to unexpected behavior. The flaw also aligns with ATT&CK technique T1499.004, Network Denial of Service, as it allows local users to cause system-wide disruption through kernel-level memory manipulation. The impact extends beyond simple system instability since the kernel crash can potentially lead to data loss, system downtime, and compromise of the overall system integrity. The vulnerability is particularly concerning because it requires no special privileges beyond local user access, making it exploitable by any user with shell access to the system.
Mitigation strategies for this vulnerability should include immediate patching of affected FreeBSD versions to the latest stable releases that contain the necessary kernel fixes. System administrators should also implement monitoring solutions to detect unusual memory allocation patterns that might indicate exploitation attempts. Additionally, the principle of least privilege should be enforced to limit local user access where possible, and regular security audits should be conducted to identify similar integer handling issues within the kernel codebase. The vulnerability underscores the importance of rigorous input validation and integer type consistency in kernel-level programming, particularly when dealing with system calls that manipulate critical memory structures.