CVE-2012-5640 in thttpd
Summary
by MITRE
thttpd has a local DoS vulnerability via specially-crafted .htpasswd files
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Analysis
by VulDB Data Team • 12/29/2024
The thttpd web server vulnerability identified as CVE-2012-5640 represents a significant local denial of service flaw that can be exploited through maliciously crafted .htpasswd files. This vulnerability resides within the authentication handling mechanism of thttpd, a lightweight web server commonly used in embedded systems and environments where minimal resource consumption is critical. The flaw specifically affects how thttpd processes authentication credentials stored in .htpasswd files, creating a condition where malformed or specially constructed entries can cause the server to crash or become unresponsive.
The technical implementation of this vulnerability stems from inadequate input validation within thttpd's authentication module. When the web server encounters a .htpasswd file containing malformed entries or entries that exceed expected parameter limits, the parsing routine fails to properly handle the edge cases, leading to memory corruption or stack overflow conditions. This behavior aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-125, which addresses out-of-bounds read vulnerabilities. The vulnerability operates at the application level within the web server's authentication subsystem, making it particularly dangerous as it can be triggered by any user with write access to the web server's configuration directories or by an attacker who can influence the contents of .htpasswd files through various attack vectors.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by malicious actors to maintain persistent denial of service conditions against targeted systems. In embedded environments where thttpd is commonly deployed, such as network appliances, routers, or IoT devices, this vulnerability can result in complete service unavailability, potentially compromising network operations and system accessibility. The local nature of the vulnerability means that exploitation typically requires either physical access to the system or the ability to write files to directories where thttpd operates, but this still represents a critical risk in environments where privilege escalation or file system manipulation is possible. Attackers can craft .htpasswd files containing maliciously formatted entries that trigger the vulnerable code path, causing the web server process to terminate unexpectedly or enter an unrecoverable state.
Mitigation strategies for CVE-2012-5640 should focus on both immediate patching and operational hardening measures. The most effective solution involves upgrading to a patched version of thttpd that properly validates .htpasswd file contents and implements robust error handling for malformed entries. Organizations should also implement strict file access controls and monitoring for changes to authentication files, as recommended by the MITRE ATT&CK framework's privilege escalation and persistence techniques. Additional protective measures include implementing file integrity monitoring solutions that can detect unauthorized modifications to .htpasswd files, restricting write permissions to web server configuration directories, and employing network segmentation to limit potential attack vectors. Security teams should also consider implementing intrusion detection systems that can identify patterns of .htpasswd file manipulation and establish incident response procedures for handling potential exploitation attempts. The vulnerability demonstrates the importance of input validation in authentication systems and highlights the need for comprehensive testing of edge cases in security-critical applications.