CVE-2019-6989 in TL-WR940N
Summary
by MITRE
TP-Link TL-WR940N is vulnerable to a stack-based buffer overflow, caused by improper bounds checking by the ipAddrDispose function. By sending specially crafted ICMP echo request packets, a remote authenticated attacker could overflow a buffer and execute arbitrary code on the system with elevated privileges.
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Analysis
by VulDB Data Team • 06/26/2024
The TP-Link TL-WR940N router presents a critical stack-based buffer overflow vulnerability that stems from inadequate input validation within the ipAddrDispose function. This flaw represents a fundamental failure in memory management practices where the device fails to properly bounds-check user-supplied data before processing it. The vulnerability specifically manifests when the router processes ICMP echo request packets, which are commonly used for network diagnostics and connectivity testing. The improper implementation allows an attacker to manipulate the buffer size through crafted packet contents, leading to potential memory corruption that can be exploited for code execution.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with common attack methodologies documented in the ATT&CK framework under defensive evasion and privilege escalation techniques. The ipAddrDispose function lacks proper input sanitization and buffer size verification, creating a predictable overflow condition that can be triggered remotely by authenticated users. This authentication requirement reduces the attack surface compared to fully unauthenticated exploits but still represents a significant security risk since legitimate network users could potentially leverage this vulnerability. The stack-based nature of the overflow means that the attacker can overwrite return addresses and function pointers, enabling arbitrary code execution with the privileges of the affected process, which typically runs with elevated system privileges.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise and potential network infiltration. Once exploited, the attacker gains a foothold that can be used for persistent access, data exfiltration, or as a launching point for further attacks within the local network. The router's role as a network gateway makes it a particularly attractive target for attackers seeking to establish backdoors or pivot to other network devices. The vulnerability affects the device's core network processing functionality, potentially disrupting services or creating denial of service conditions while simultaneously providing unauthorized access to sensitive network information.
Mitigation strategies for this vulnerability should encompass both immediate and long-term security measures. The most effective immediate solution involves applying the vendor-provided firmware update that addresses the buffer overflow in the ipAddrDispose function through proper bounds checking and input validation. Network administrators should also implement ingress filtering to limit ICMP traffic from untrusted sources and consider deploying intrusion detection systems that can identify anomalous ICMP packet patterns. The vulnerability demonstrates the importance of secure coding practices and proper memory management as outlined in CWE-121, which specifically addresses stack-based buffer overflow conditions. Organizations should also conduct regular security assessments of network infrastructure devices and maintain updated vulnerability management processes to identify and remediate similar issues before they can be exploited by malicious actors.