CVE-2007-1741 in HTTP Server
Summary
by MITRE
Multiple race conditions in suexec in Apache HTTP Server (httpd) 2.2.3 between directory and file validation, and their usage, allow local users to gain privileges and execute arbitrary code by renaming directories or performing symlink attacks. NOTE: the researcher, who is reliable, claims that the vendor disputes the issue because "the attacks described rely on an insecure server configuration" in which the user "has write access to the document root."
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2007-1741 represents a critical privilege escalation flaw within the Apache HTTP Server's suexec module version 2.2.3. This issue stems from race conditions that occur during the validation process of directories and files, creating exploitable temporal windows where malicious actors can manipulate the system state. The suexec module is designed to allow web applications to run with the privileges of the file owner rather than the web server user, providing an essential security boundary in shared hosting environments. However, the implementation contains fundamental flaws that undermine this security model.
The technical flaw manifests through race conditions between directory and file validation checks within the suexec execution flow. When Apache processes requests through suexec, it performs validation steps that check directory permissions and file ownership before executing scripts. Attackers can exploit these race conditions by rapidly renaming directories or creating symbolic links during the validation window, effectively bypassing the intended security controls. This vulnerability specifically targets the timing gap between when the system validates directory access and when it actually executes the file, allowing attackers to substitute their own malicious files or directories during this critical period.
The operational impact of this vulnerability is severe as it enables local users to escalate privileges and execute arbitrary code on the target system. The attack requires only local access and can be performed through directory renaming or symlink manipulation techniques. The vulnerability's exploitation potential is particularly concerning in shared hosting environments where multiple users may have write access to the document root directory. According to the researcher's findings, the attack vector involves creating a symlink that points to a privileged file or directory, then quickly renaming it during the validation window to gain elevated privileges.
The security implications extend beyond simple privilege escalation, as this vulnerability can lead to complete system compromise. The attack methodology aligns with common exploitation techniques documented in the attack framework, specifically targeting the timing and validation phases of system operations. This vulnerability is categorized under CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, a well-known class of security flaws that have been extensively documented in industry security standards. The flaw demonstrates how seemingly minor timing issues in system validation can create critical security breaches.
The vendor's response to this issue, while acknowledging the vulnerability exists, attempts to dismiss it by citing insecure server configurations where users have write access to the document root. This perspective reflects a common debate in security circles about the responsibility for secure configurations versus the need for robust software implementations. However, the vulnerability remains exploitable in many real-world scenarios where administrators may not fully understand the implications of allowing write access to document roots, particularly in shared hosting environments. The attack's success is not dependent on complex network conditions but rather on the inherent timing flaws in the validation process. Organizations should implement proper access controls and secure configuration practices to prevent attackers from gaining the necessary privileges to exploit this vulnerability. The recommended mitigations include restricting write access to document root directories, implementing proper file system permissions, and ensuring that suexec is properly configured to avoid the race condition scenarios. Additionally, system administrators should consider upgrading to patched versions of Apache HTTP Server where these race conditions have been addressed through improved validation timing and more robust security controls.