CVE-2004-2372 in Bochs
Summary
by MITRE
Buffer overflow in Bochs before 2.1.1, if installed setuid, allows local users to execute arbitrary code via a long HOME environment variable, which is used if the .bochsrc, bochsrc, and bochsrc.txt cannot be found in a known path. NOTE: some external documents recommend that Bochs be installed setuid root, so this should be treated as a vulnerability.
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Analysis
by VulDB Data Team • 06/29/2018
The vulnerability described in CVE-2004-2372 represents a critical buffer overflow flaw within the Bochs x86 emulator software, specifically affecting versions prior to 2.1.1. This issue arises from improper input validation when processing environment variables, creating a pathway for local privilege escalation attacks. The vulnerability is particularly concerning because Bochs was often installed with setuid root permissions, a practice recommended by some external documentation, which amplifies the security implications significantly. When the emulator runs with elevated privileges, any buffer overflow exploit targeting it can potentially lead to complete system compromise.
The technical flaw occurs in the way Bochs handles the HOME environment variable during its initialization process. When the emulator attempts to locate configuration files such as .bochsrc, bochsrc, or bochsrc.txt in standard locations and fails to find them, it falls back to using the HOME environment variable to determine where to search for these files. However, the code fails to properly validate the length of this environment variable, allowing attackers to provide an excessively long string that overflows the allocated buffer. This buffer overflow occurs in the memory management routines that handle environment variable processing, where the fixed-size buffer cannot accommodate the extended input, leading to memory corruption that can be exploited to execute arbitrary code.
The operational impact of this vulnerability is severe for systems running vulnerable versions of Bochs with setuid root permissions. Local attackers who can control the HOME environment variable can leverage this flaw to gain elevated privileges and execute malicious code with root-level access. The attack vector is relatively straightforward since it only requires the ability to set environment variables, which is typically possible for any local user. This makes the vulnerability particularly dangerous in multi-user environments where users may not be trusted, as any compromised account can potentially be used to escalate privileges and take control of the entire system. The vulnerability essentially provides a direct path from local user access to root privileges through a simple environment variable manipulation.
Mitigation strategies for this vulnerability involve several layers of protection that align with established security practices. The primary recommendation is to upgrade to Bochs version 2.1.1 or later, where the buffer overflow has been addressed through proper input validation and bounds checking. Organizations should also avoid installing Bochs with setuid root permissions, as this practice fundamentally increases the attack surface and potential impact of such vulnerabilities. Security hardening measures should include implementing proper environment variable validation and sanitization, as well as employing runtime protection mechanisms such as stack canaries and address space layout randomization. Additionally, system administrators should conduct regular vulnerability assessments to identify and remediate similar issues in other setuid applications, following the principle of least privilege and ensuring that applications only run with necessary permissions. This vulnerability exemplifies the importance of proper input validation and the dangers of setuid applications, aligning with CWE-121 buffer overflow categories and ATT&CK techniques related to privilege escalation and code execution.