CVE-2017-15637 in WVR
Summary
by MITRE
TP-Link WVR, WAR and ER devices allow remote authenticated administrators to execute arbitrary commands via command injection in the pptphellointerval variable in the pptp_server.lua file.
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Analysis
by VulDB Data Team • 12/22/2019
The vulnerability identified as CVE-2017-15637 affects TP-Link WVR, WAR, and ER series network devices, representing a critical command injection flaw that enables remote authenticated administrators to execute arbitrary code on affected systems. This vulnerability resides within the pptp_server.lua file where the pptphellointerval variable is improperly handled, creating a pathway for malicious command execution. The flaw specifically targets devices that implement PPTP (Point-to-Point Tunneling Protocol) server functionality, making it particularly dangerous for network infrastructure devices that rely on this protocol for remote access services.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the pptp_server.lua script. When an authenticated administrator modifies the pptphellointerval parameter, the system fails to properly escape or filter special characters that could be interpreted as shell commands. This allows an attacker with administrative privileges to inject malicious commands that get executed within the context of the system's shell. The vulnerability is classified as a command injection flaw under CWE-77, which specifically addresses situations where user-supplied data is directly incorporated into shell commands without proper sanitization. The attack vector requires an authenticated administrative session, but once exploited, the attacker gains the ability to execute arbitrary commands with the privileges of the affected service account.
From an operational impact perspective, this vulnerability presents a severe risk to network infrastructure security as it allows attackers who have gained administrative access to escalate their privileges and execute arbitrary code on the target devices. The affected TP-Link devices typically serve as network gateways, firewalls, or routing appliances, making them critical components of network security infrastructure. Successful exploitation could lead to complete system compromise, enabling attackers to establish persistent backdoors, exfiltrate network data, or use the compromised device as a launch point for further attacks against internal network segments. The vulnerability also aligns with ATT&CK technique T1059.001 for command and scripting interpreter, specifically shell scripting, where adversaries use command-line interfaces to execute malicious commands on compromised systems.
The exploitation of this vulnerability requires an attacker to first obtain legitimate administrative credentials, which may be achieved through credential theft, brute force attacks, or other initial compromise techniques. Once authenticated, the attacker can modify the pptphellointerval parameter through the device's web interface or API endpoints, injecting malicious commands that are then executed by the system's shell. The lack of proper input validation means that commands such as semicolons, pipes, or other shell metacharacters can be passed directly to the underlying shell, creating a path for arbitrary code execution. Organizations should consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities, while also ensuring that administrative credentials are protected through multi-factor authentication and regular credential rotation. The vulnerability underscores the importance of input validation and output encoding practices as outlined in OWASP Top 10 and other security frameworks, emphasizing that all user-supplied data must be properly sanitized before being processed by system commands or interpreted by shell environments.