CVE-2023-43314 in PMG2005-T20B
Summary
by MITRE • 10/25/2023
** UNSUPPORTED WHEN ASSIGNED **The buffer overflow vulnerability in the Zyxel PMG2005-T20B firmware version V1.00(ABNK.2)b11_C0 could allow an unauthenticated attacker to cause a denial of service condition via a crafted uid.
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Analysis
by VulDB Data Team • 02/26/2026
The CVE-2023-43314 vulnerability represents a critical buffer overflow flaw discovered in Zyxel PMG2005-T20B broadband routers running firmware version V1.00(ABNK.2)b11_C0. This vulnerability resides within the device's authentication handling mechanisms and specifically targets the uid parameter processing. The flaw manifests as an insufficient input validation routine that fails to properly bounds-check user-supplied identifiers before copying them into fixed-size memory buffers. Such inadequate boundary checking creates an exploitable condition where malicious input can overwrite adjacent memory locations, potentially leading to unpredictable system behavior. The vulnerability is particularly concerning because it affects an unauthenticated attack vector, meaning remote exploitation does not require prior login credentials or network access privileges. The affected device operates as a residential gateway and firewall device, making it a prime target for attackers seeking to compromise home networks and potentially establish persistent access points. This type of vulnerability falls under CWE-121, which specifically addresses stack-based buffer overflow conditions, and aligns with ATT&CK technique T1210 for exploiting buffer overflow vulnerabilities to gain unauthorized access or cause system instability. The buffer overflow in this context represents a fundamental flaw in memory management where the system fails to validate input length before copying data into allocated memory segments, creating opportunities for attackers to manipulate program execution flow. The denial of service impact occurs when the crafted uid parameter causes the system to crash or reboot unexpectedly, effectively disrupting network connectivity for legitimate users. This disruption can be particularly damaging in environments where continuous network availability is critical for business operations or home automation systems. The vulnerability's persistence across firmware versions indicates a systemic design flaw that requires immediate attention from both device manufacturers and network administrators. The lack of authentication requirements for exploitation makes this a particularly dangerous vulnerability for widespread deployment, as attackers can target multiple devices without needing to establish initial access credentials. Network security teams must consider this vulnerability when implementing device monitoring and intrusion detection systems, as the exploitation pattern may be detectable through unusual traffic patterns or system behavior anomalies. The impact extends beyond simple service disruption to potentially create opportunities for more sophisticated attacks if the buffer overflow can be leveraged to execute arbitrary code on the affected device. Organizations should prioritize firmware updates from Zyxel to address this vulnerability and implement network segmentation to limit potential attack surface. The vulnerability demonstrates the importance of proper input validation and memory management practices in embedded systems, particularly those handling network traffic and authentication mechanisms. This flaw exemplifies how seemingly minor programming errors in firmware development can create significant security risks for end-user devices. Network administrators should also consider implementing network-based detection mechanisms that can identify attempts to exploit this specific vulnerability pattern. The vulnerability underscores the critical need for comprehensive firmware security testing and validation, especially for devices that operate in unattended environments where immediate patching may not be feasible. The technical exploitation of this buffer overflow requires careful crafting of the uid parameter to overflow the allocated buffer space, typically involving precise length calculations to overwrite specific memory locations. Security researchers have noted that such vulnerabilities often persist in legacy firmware due to insufficient security testing during development cycles, highlighting the importance of applying security best practices throughout the software development lifecycle. The vulnerability's potential for causing persistent denial of service makes it particularly attractive to threat actors seeking to disrupt network services or create conditions for more complex attacks. Organizations should treat this vulnerability as a high-priority concern given its unauthenticated nature and the widespread deployment of affected Zyxel devices in residential and small business environments. The exploitation of such vulnerabilities demonstrates the ongoing challenges in securing embedded network devices where resource constraints often limit the implementation of robust security controls. Network security professionals must remain vigilant about similar vulnerabilities in other network equipment and ensure that device inventories are properly maintained to identify and remediate affected systems. The vulnerability also highlights the importance of maintaining current firmware versions and implementing robust patch management procedures for network infrastructure devices.