CVE-2020-25691 in darkhttpd
Summary
by MITRE • 04/02/2022
A flaw was found in darkhttpd. Invalid error handling allows remote attackers to cause denial-of-service by accessing a file with a large modification date. The highest threat from this vulnerability is to system availability.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 04/05/2022
The vulnerability identified as CVE-2020-25691 resides within the darkhttpd web server implementation, representing a critical denial-of-service weakness that stems from inadequate error handling mechanisms. This flaw specifically manifests when remote attackers manipulate file modification timestamps to extreme values, particularly those with large modification dates. The darkhttpd server, designed as a lightweight alternative to full-featured web servers, processes file metadata during request handling but fails to properly validate or sanitize timestamp values that exceed normal operational parameters. This deficiency creates a condition where maliciously crafted file access requests can trigger unexpected server behavior.
The technical exploitation of this vulnerability leverages the server's inability to handle excessively large modification dates gracefully, causing the web server to enter a state where it cannot properly process subsequent requests or maintain normal service operations. When a file with an anomalous timestamp is accessed, the server's internal processing logic becomes overwhelmed or enters an infinite loop, resulting in complete service unavailability for legitimate users. This behavior aligns with CWE-248, which addresses improper exception handling in software systems, and demonstrates how seemingly benign input validation failures can cascade into critical system stability issues. The vulnerability operates at the application layer, affecting the web server's core functionality without requiring authentication or specialized privileges.
From an operational impact perspective, this vulnerability presents a significant threat to system availability and service reliability, particularly in environments where darkhttpd serves as a primary web server for static content delivery. Organizations relying on this lightweight server for internal or external web hosting face potential service disruption that could affect business operations, user access, and overall system uptime. The attack vector is particularly concerning because it requires minimal technical expertise to execute, making it accessible to a broad range of threat actors. The vulnerability's impact severity classifies it as high-risk due to its ability to completely disable server functionality, with recovery typically requiring manual intervention and server restart operations.
Mitigation strategies for CVE-2020-25691 should prioritize immediate patching of affected darkhttpd installations, as the vulnerability cannot be effectively addressed through configuration changes alone. System administrators should implement monitoring solutions to detect unusual file modification patterns and establish automated alerting for timestamp anomalies that could indicate exploitation attempts. Network-level protections such as rate limiting and connection throttling can help reduce the impact of potential DoS attacks while patches are deployed. Additionally, organizations should consider implementing redundant web server configurations to maintain service availability during patch deployment windows. The vulnerability's classification under ATT&CK technique T1499.004 highlights its potential for abuse in service disruption campaigns, emphasizing the need for comprehensive incident response planning and network segmentation strategies to limit the attack surface and contain potential exploitation attempts.