CVE-2001-1496 in thttpd
Summary
by MITRE
Off-by-one buffer overflow in Basic Authentication in Acme Labs thttpd 1.95 through 2.20 allows remote attackers to cause a denial of service and possibly execute arbitrary code.
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Analysis
by VulDB Data Team • 09/24/2025
The vulnerability identified as CVE-2001-1496 represents a critical buffer overflow condition within the Acme Labs thttpd web server software versions 1.95 through 2.20. This flaw specifically affects the Basic Authentication implementation mechanism, which is fundamental to web server security protocols for user access control. The issue manifests as an off-by-one error in the handling of authentication credentials, where the software fails to properly validate input boundaries when processing user authentication requests. This type of vulnerability falls under the CWE-121 category of buffer overflow conditions, specifically involving stack-based buffer overflows that can lead to unpredictable behavior and system compromise.
The technical exploitation of this vulnerability occurs when remote attackers send specially crafted authentication requests that exceed the allocated buffer space by exactly one byte. This seemingly minor deviation triggers memory corruption that can be leveraged to overwrite adjacent memory locations, potentially allowing attackers to execute arbitrary code on the affected system. The denial of service aspect of this vulnerability is particularly concerning as it can be triggered without authentication, making it accessible to any remote attacker who can establish network connectivity to the vulnerable web server. The buffer overflow in the Basic Authentication module creates a pathway for attackers to manipulate the execution flow of the web server process through stack corruption.
The operational impact of CVE-2001-1496 extends beyond simple service disruption to potentially enable full system compromise when exploited successfully. Web servers running vulnerable versions of thttpd become susceptible to remote code execution attacks, which can result in unauthorized access to sensitive data, system control, and potential lateral movement within network environments. The vulnerability's presence in Basic Authentication means that any web application relying on this authentication mechanism for protecting resources becomes vulnerable to attack. This represents a significant risk for organizations that depend on thttpd for serving web content, particularly in environments where web applications handle sensitive user information or business-critical data.
Mitigation strategies for this vulnerability require immediate patching of affected thttpd installations to versions that address the buffer overflow condition in the Basic Authentication implementation. System administrators should also implement network-level restrictions to limit access to web server functionality and monitor for unusual authentication attempts that might indicate exploitation attempts. The vulnerability's classification under ATT&CK technique T1190 for exploitation of remote services and T1075 for use of legitimate credentials highlights the need for comprehensive monitoring of authentication patterns and network traffic analysis. Additionally, implementing proper input validation and boundary checking mechanisms in web server configurations can help prevent similar issues from occurring in other software components that may be subject to similar buffer overflow conditions.