CVE-2008-2636 in Linksys Wrh54g Router
Summary
by MITRE
The HTTP service on the Cisco Linksys WRH54G with firmware 1.01.03 allows remote attackers to cause a denial of service (management interface outage) or possibly execute arbitrary code via a URI that begins with a "/./" sequence, contains many instances of a "front_page" sequence, and ends with a ".asp" sequence.
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Analysis
by VulDB Data Team • 11/16/2017
The vulnerability identified as CVE-2008-2636 affects the HTTP service implementation within Cisco Linksys WRH54G wireless routers running firmware version 1.01.03. This represents a critical security flaw that demonstrates a classic buffer overflow condition within the web management interface processing logic. The vulnerability stems from inadequate input validation and sanitization of Uniform Resource Identifier (URI) parameters, creating an exploitable condition that can be leveraged by remote attackers without authentication. The specific attack vector involves crafting malicious URIs that begin with "/./" sequences, incorporate multiple instances of "front_page" strings, and conclude with ".asp" extensions, exploiting the router's insufficient handling of these malformed requests.
The technical exploitation mechanism operates through a combination of directory traversal and resource exhaustion techniques that target the web server's parsing routines. The "/./" sequence initially appears to be a benign path traversal attempt but when combined with repeated "front_page" occurrences and ending with ".asp" extensions, it creates a payload that can overwhelm the HTTP service's memory allocation mechanisms. This particular combination of sequences triggers an improper handling of the request parsing logic, leading to stack corruption or heap-based buffer overflows. The vulnerability falls under CWE-121, which describes heap-based buffer overflow conditions, and CWE-122, which covers stack-based buffer overflow scenarios. The attack pattern aligns with ATT&CK technique T1203, which involves exploitation of software vulnerabilities for privilege escalation and system compromise.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable remote code execution on affected devices. When exploited successfully, attackers can gain control over the router's management interface and potentially execute arbitrary commands with elevated privileges. The management interface outage represents the most immediate consequence, rendering the device inaccessible to authorized administrators and disrupting network connectivity. However, the potential for remote code execution introduces more severe implications, as attackers could install backdoors, modify routing tables, or establish persistent access points within the network infrastructure. The vulnerability affects the device's core functionality by compromising the integrity of its web-based administrative interface, which serves as the primary means for configuration and monitoring.
Mitigation strategies for this vulnerability require immediate firmware updates from Cisco to address the underlying parsing logic flaws. Network administrators should implement network segmentation and access controls to limit exposure of affected devices to untrusted networks. The implementation of web application firewalls and intrusion detection systems can help detect and block malicious URI patterns targeting this specific vulnerability. Additionally, disabling unnecessary web management interfaces and restricting access to trusted IP ranges provides layered defense measures. The vulnerability demonstrates the importance of input validation in network device implementations and highlights the need for regular security assessments of embedded systems. Organizations should also consider implementing network monitoring solutions to detect unusual traffic patterns that may indicate exploitation attempts, particularly focusing on malformed URI requests that follow the specific attack pattern described in the vulnerability.