CVE-2020-9374 in TL-WR849N
Summary
by MITRE
On TP-Link TL-WR849N 0.9.1 4.16 devices, a remote command execution vulnerability in the diagnostics area can be exploited when an attacker sends specific shell metacharacters to the panel's traceroute feature.
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Analysis
by VulDB Data Team • 07/20/2024
The CVE-2020-9374 vulnerability represents a critical remote command execution flaw affecting TP-Link TL-WR849N routers running firmware versions 0.9.1 and 4.16. This vulnerability resides within the device's diagnostics functionality, specifically targeting the traceroute feature that allows administrators and attackers to trace network paths. The flaw demonstrates poor input validation and sanitization practices within the router's web interface, creating an avenue for malicious actors to inject and execute arbitrary shell commands on the affected device. The vulnerability is particularly concerning because it operates at the diagnostic level where legitimate network troubleshooting tools are accessible, making it difficult to distinguish between benign administrative activity and malicious exploitation attempts.
The technical implementation of this vulnerability stems from insufficient sanitization of user-supplied input passed to the traceroute functionality. When an attacker crafts malicious input containing shell metacharacters such as semicolons, ampersands, or command separators, these characters are not properly escaped or filtered before being processed by the underlying shell. This allows the system to interpret and execute the injected commands as part of the traceroute operation, effectively bypassing the intended security boundaries of the diagnostic interface. The vulnerability is classified as a command injection flaw that aligns with CWE-77 and CWE-94 categories, representing a direct path to arbitrary code execution within the router's operating environment. This type of vulnerability enables attackers to gain full control over the device, potentially allowing them to modify network configurations, intercept traffic, or establish persistent access points within the network.
The operational impact of CVE-2020-9374 extends beyond simple device compromise, as it provides attackers with a foothold for broader network infiltration. Once an attacker successfully exploits this vulnerability, they can leverage the compromised router as a pivot point to launch further attacks against internal network resources, potentially escalating privileges and accessing sensitive data. The vulnerability's remote exploitability means that attackers do not require physical access or network proximity to the device, making it particularly dangerous in environments where network security is not properly segmented. This flaw can be exploited through standard web browser interfaces, making it accessible to attackers with minimal technical expertise. From an attack framework perspective, this vulnerability maps to multiple ATT&CK techniques including T1059.001 for command and scripting interpreter and T1021.001 for remote services, enabling attackers to establish persistent access and maintain control over the compromised device for extended periods.
Mitigation strategies for CVE-2020-9374 require immediate firmware updates from TP-Link to address the underlying input validation issues. Organizations should implement network segmentation to isolate affected devices from critical infrastructure, particularly by placing routers in separate network zones with restricted access controls. Network monitoring solutions should be configured to detect unusual traceroute activity or command execution patterns that might indicate exploitation attempts. Security administrators should disable unnecessary diagnostic features when not actively required and implement web application firewalls to filter potentially malicious input before it reaches the vulnerable components. Regular vulnerability assessments and penetration testing should be conducted to identify similar input validation flaws in other network infrastructure devices, as this vulnerability demonstrates a pattern of inadequate sanitization practices that may exist in other router models or network equipment. Additionally, implementing network access controls and monitoring for unauthorized access attempts can help detect and prevent exploitation attempts before they succeed.