CVE-2025-4139 in EX6120
Summary
by MITRE • 05/01/2025
A vulnerability classified as critical was found in Netgear EX6120 1.0.0.68. Affected by this vulnerability is the function fwAcosCgiInbound. The manipulation of the argument host leads to buffer overflow. The attack can be launched remotely. The vendor was contacted early about this disclosure but did not respond in any way.
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Analysis
by VulDB Data Team • 06/23/2025
The vulnerability identified as CVE-2025-4139 represents a critical buffer overflow flaw within the Netgear EX6120 wireless router firmware version 1.0.0.68. This issue resides in the fwAcosCgiInbound function which processes incoming network requests, making it a prime target for remote exploitation. The specific vector of attack involves manipulation of the host argument parameter, which when improperly handled leads to memory corruption that can be leveraged by malicious actors. The vulnerability's classification as critical stems from its remote exploitability and the potential for arbitrary code execution within the affected device's operating environment.
The technical implementation of this buffer overflow vulnerability demonstrates a classic programming error where input validation is insufficiently enforced in the processing of network requests. When the host argument is passed to the fwAcosCgiInbound function, the firmware fails to properly bounds-check the input data before copying it into a fixed-size buffer. This allows an attacker to overflow the allocated memory space and potentially overwrite adjacent memory locations including return addresses and control data. The CWE-121 classification applies here as the vulnerability involves stack-based buffer overflow conditions where insufficient boundary checking enables attackers to write beyond allocated buffer boundaries. Such flaws are particularly dangerous in embedded network devices where memory corruption can lead to complete system compromise.
The operational impact of this vulnerability extends beyond simple denial of service scenarios as it enables remote code execution capabilities that could allow attackers to gain complete administrative control of the affected router. Network administrators face significant risk since the vulnerability can be exploited without requiring physical access to the device, making it particularly concerning for enterprise and residential deployments. The attack surface is broad given that the vulnerability affects a widely deployed networking device, potentially exposing thousands of devices to remote compromise. This type of vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1021.001 for remote services, as attackers could leverage the compromised device for further network reconnaissance and lateral movement. The lack of vendor response to early disclosure attempts compounds the risk, leaving affected users without official patches or mitigation guidance during the vulnerability's active window.
Mitigation strategies for CVE-2025-4139 should prioritize immediate network segmentation and monitoring of affected devices. Organizations should implement network access controls to limit exposure of the vulnerable router to untrusted networks and establish network monitoring to detect anomalous traffic patterns that may indicate exploitation attempts. The most effective long-term solution involves firmware updates from Netgear, though given the vendor's lack of response, security teams may need to consider alternative approaches such as network-level firewalls, intrusion detection systems, or device isolation. Additionally, network administrators should conduct thorough vulnerability assessments of all networked devices to identify similar patterns of insufficient input validation that could present analogous risks. The vulnerability highlights the importance of maintaining current firmware versions and implementing robust security practices for network infrastructure devices that often remain unpatched due to their perceived low risk.