CVE-2022-26641 in TL-WR840N
Summary
by MITRE • 03/29/2022
TP-LINK TL-WR840N(ES)_V6.20 was discovered to contain a buffer overflow via the httpRemotePort parameter.
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Analysis
by VulDB Data Team • 03/31/2022
The vulnerability identified as CVE-2022-26641 affects TP-LINK TL-WR840N(ES)_V6.20 routers, representing a critical buffer overflow flaw that resides within the device's web interface handling mechanism. This issue manifests through the httpRemotePort parameter, which serves as an entry point for malicious input manipulation. The vulnerability stems from inadequate input validation and bounds checking within the router's firmware, specifically in how it processes HTTP requests containing the remote port configuration parameter. When an attacker submits a crafted payload through this parameter, the system fails to properly validate the input length, allowing malicious data to overflow into adjacent memory regions.
The technical implementation of this buffer overflow occurs within the router's HTTP server component that manages administrative configurations. The httpRemotePort parameter is processed without sufficient boundary checks, enabling attackers to exceed the allocated buffer space and overwrite critical memory segments including return addresses, function pointers, or other control data structures. This flaw falls under CWE-121, which specifically addresses stack-based buffer overflow conditions, and potentially CWE-122 for heap-based buffer overflows depending on the exact memory layout. The vulnerability is particularly concerning because it operates within the web administration interface, meaning remote exploitation is possible without requiring physical access to the device.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it presents a significant attack surface for privilege escalation and remote code execution. An attacker who successfully exploits this buffer overflow could potentially execute arbitrary code on the affected router, gain full administrative control over the device, and subsequently compromise the entire network segment. The attack vector requires no authentication for exploitation, making it particularly dangerous as it allows for unauthorized access through the standard web interface. This vulnerability directly aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter, as successful exploitation could enable command execution on the affected system. Network reconnaissance activities could leverage this vulnerability to establish persistent access points within the target network.
Mitigation strategies for CVE-2022-26641 should prioritize immediate firmware updates from TP-LINK, as the manufacturer has likely released patches addressing this specific buffer overflow condition. Network segmentation and firewall rules should be implemented to restrict access to the router's administrative interface from untrusted networks, while also monitoring for unusual traffic patterns that might indicate exploitation attempts. Network administrators should consider disabling remote administration features entirely when not required, and implement additional security controls such as intrusion detection systems that can identify malformed HTTP requests targeting the vulnerable parameter. Regular vulnerability assessments should include checking for outdated firmware versions, particularly on legacy devices that may not receive regular security updates. The vulnerability also highlights the importance of implementing robust input validation practices, including the use of modern programming techniques that prevent buffer overflows through stack canaries, address space layout randomization, and other exploit mitigations that are standard in contemporary security frameworks.