CVE-2018-3951 in TL-R600VPN
Summary
by MITRE
An exploitable remote code execution vulnerability exists in the HTTP header-parsing function of the TP-Link TL-R600VPN HTTP Server. A specially crafted HTTP request can cause a buffer overflow, resulting in remote code execution on the device. An attacker can send an authenticated HTTP request to trigger this vulnerability.
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Analysis
by VulDB Data Team • 06/12/2023
The CVE-2018-3951 vulnerability represents a critical remote code execution flaw in the TP-Link TL-R600VPN device's HTTP server implementation. This vulnerability stems from improper input validation within the HTTP header parsing functionality, creating a condition where maliciously crafted HTTP requests can trigger buffer overflow conditions. The affected device operates a web-based management interface that processes HTTP headers without adequate bounds checking, allowing attackers to manipulate memory layout through carefully constructed request parameters. The vulnerability specifically targets the HTTP server component that handles incoming web requests from management interfaces, making it particularly dangerous for network administrators who rely on web-based device management. The buffer overflow occurs during the parsing of HTTP headers, where the server fails to properly validate the length of incoming header data before copying it into fixed-size memory buffers. This fundamental flaw in input sanitization creates a pathway for arbitrary code execution, enabling attackers to gain complete control over the affected device's operational environment.
The technical exploitation of this vulnerability requires an authenticated HTTP request, meaning that attackers must first establish valid credentials to access the device's web management interface. However, once authenticated, the attacker can craft a specific HTTP request containing oversized header data that exceeds the allocated buffer space. This overflow condition typically results in memory corruption that can be leveraged to overwrite critical program execution pointers or return addresses, ultimately allowing the attacker to inject and execute malicious code within the device's memory space. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of how insufficient input validation can lead to privilege escalation and full system compromise. The attack vector follows the pattern described in the MITRE ATT&CK framework under T1059 for command and script injection, where an attacker can execute arbitrary commands on the target system through the vulnerable web interface.
The operational impact of CVE-2018-3951 extends beyond simple device compromise, as the TP-Link TL-R600VPN serves as a critical network infrastructure component providing secure remote access capabilities. When compromised, the device can be used as a pivot point for further network infiltration, allowing attackers to establish persistent access to internal networks and potentially escalate privileges to other connected systems. The vulnerability affects devices that are commonly deployed in remote office environments where administrators may have limited physical access, making the remote exploitation capability particularly concerning. Network security teams face challenges in detecting this attack due to the legitimate nature of HTTP requests and the fact that the vulnerability requires authentication, which makes it harder to distinguish from normal administrative activity. The affected device's role in VPN connectivity means that successful exploitation could result in complete network traffic interception and manipulation, potentially compromising sensitive data flowing through the network. Organizations using this device in production environments should consider the potential for lateral movement and data exfiltration following initial compromise.
Mitigation strategies for CVE-2018-3951 should prioritize immediate firmware updates from TP-Link to address the underlying buffer overflow condition in the HTTP header parsing implementation. Network administrators should implement strict access controls including multi-factor authentication and limit administrative access to the device to trusted personnel only. Additional network segmentation measures can help contain potential compromise by isolating the device from critical internal systems. The implementation of web application firewalls and intrusion detection systems can help monitor for suspicious HTTP header patterns that may indicate exploitation attempts. Regular security audits of network infrastructure devices should include verification of firmware versions and patch status to prevent similar vulnerabilities from remaining unaddressed. Organizations should also consider implementing network monitoring solutions that can detect anomalous authentication patterns or unusual HTTP request behaviors that might indicate exploitation attempts. The vulnerability demonstrates the importance of secure coding practices and input validation, particularly in network-facing services where authentication is required. Security teams should also establish incident response procedures specifically addressing device compromise scenarios to ensure rapid response and containment when such vulnerabilities are exploited in the wild.