CVE-2003-0955 in OpenBSD
Summary
by MITRE
OpenBSD kernel 3.3 and 3.4 allows local users to cause a denial of service (kernel panic) and possibly execute arbitrary code in 3.4 via a program with an invalid header that is not properly handled by (1) ibcs2_exec.c in the iBCS2 emulation (compat_ibcs2) or (2) exec_elf.c, which leads to a stack-based buffer overflow.
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Analysis
by VulDB Data Team • 07/09/2024
The vulnerability identified as CVE-2003-0955 represents a critical security flaw in the OpenBSD kernel versions 3.3 and 3.4 that affects the system's ability to handle executable files with malformed headers. This issue stems from inadequate input validation within the kernel's binary execution handling mechanisms, specifically within the iBCS2 emulation layer and the ELF execution framework. The vulnerability manifests when a local user crafts a program with an invalid header structure that the kernel fails to properly process, leading to potentially catastrophic system consequences.
The technical root cause of this vulnerability lies in the improper handling of executable file headers within two key kernel components: ibcs2_exec.c responsible for iBCS2 emulation compatibility and exec_elf.c which manages ELF binary execution. When these components encounter malformed headers, they fail to validate the input properly, resulting in a stack-based buffer overflow condition. This overflow occurs because the kernel's memory management routines do not adequately check the bounds of header data before copying it into fixed-size buffers on the stack. The flaw operates at the kernel level, making it particularly dangerous as it can be exploited by local users with minimal privileges to either crash the system through kernel panic or potentially escalate privileges to execute arbitrary code.
The operational impact of this vulnerability extends beyond simple denial of service, presenting a significant risk to system integrity and availability. In kernel version 3.4, the vulnerability becomes more severe as it can potentially allow privilege escalation, enabling local attackers to execute arbitrary code with kernel-level privileges. The stack-based buffer overflow creates an exploitable condition that could be leveraged by attackers to overwrite critical memory locations, potentially leading to complete system compromise. The iBCS2 emulation layer adds additional complexity as it provides compatibility with older binary formats, making the attack surface broader and more difficult to predict.
The vulnerability aligns with CWE-121 Stack-based Buffer Overflow, which specifically addresses buffer overflows occurring in stack memory regions. This classification indicates that the issue involves a fixed-size buffer being overwritten beyond its allocated bounds, leading to memory corruption. The ATT&CK framework categorizes this under privilege escalation techniques, as the vulnerability can be exploited to gain elevated system privileges. The attack vector requires local system access and involves crafting malicious executables, making it a low-privilege but high-impact threat. Organizations running affected OpenBSD versions should implement immediate mitigations including kernel updates, system hardening measures, and monitoring for suspicious execution patterns. The vulnerability underscores the importance of proper input validation and memory safety practices in kernel code development, particularly when handling compatibility layers that process external binary data.