CVE-2022-43972 in WRT54GL
Summary
by MITRE • 01/10/2023
A null pointer dereference vulnerability exists in Linksys WRT54GL Wireless-G Broadband Router with firmware <= 4.30.18.006. A null pointer dereference in the soap_action function within the upnp binary can be triggered by an unauthenticated attacker via a malicious POST request invoking the AddPortMapping action.
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Analysis
by VulDB Data Team • 01/30/2023
The CVE-2022-43972 vulnerability represents a critical null pointer dereference flaw in the Linksys WRT54GL Wireless-G Broadband Router firmware version 4.30.18.006 and earlier. This vulnerability resides within the upnp binary component of the router's software stack, specifically in the soap_action function that handles universal plug and play protocol operations. The issue manifests when the router processes malicious POST requests that invoke the AddPortMapping action through the upnp interface, creating a condition where a null pointer is dereferenced during the processing of network traffic. This particular vulnerability affects a widely deployed consumer-grade router model that has been in use for over a decade, making it a persistent security risk for numerous network environments.
The technical exploitation of this vulnerability occurs through unauthenticated network requests that target the upnp service running on the affected router. When an attacker crafts a malicious POST request containing the AddPortMapping action, the soap_action function fails to properly validate input parameters before attempting to dereference a pointer that has not been initialized or has been set to null. This null pointer dereference results in an immediate system crash or reboot of the router, effectively causing a denial of service condition that renders the network connectivity unavailable to users. The vulnerability falls under CWE-476 which specifically addresses null pointer dereference conditions, and represents a classic example of improper input validation leading to system instability. The attack vector requires only network access to the router's upnp port, typically port 1900, making it particularly dangerous as it can be exploited remotely without requiring physical access or authentication credentials.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged as a stepping stone for more sophisticated attacks within network environments. When a router experiences repeated crashes or reboots due to this vulnerability, it disrupts network connectivity for all devices connected to the affected network, potentially affecting business operations or personal productivity. Network administrators may find their routers becoming unresponsive to management interfaces, while end users experience intermittent or complete loss of internet connectivity. The vulnerability's persistence in older firmware versions means that even networks that have migrated to newer equipment may still be vulnerable if legacy devices remain connected or if the primary router's firmware has not been updated. This type of vulnerability aligns with ATT&CK technique T1499.004 which describes network denial of service attacks, and represents a significant risk for organizations that fail to maintain current firmware versions for their network infrastructure devices.
Mitigation strategies for CVE-2022-43972 should prioritize firmware updates from Linksys or the router manufacturer, as this addresses the root cause of the vulnerability through proper pointer validation and input sanitization. Network administrators should implement firewall rules that restrict access to the upnp service port 1900 from untrusted networks, effectively blocking external exploitation attempts. Disabling upnp functionality entirely on the router, when possible, provides an additional layer of protection by eliminating the attack surface entirely. Regular network monitoring should be implemented to detect unusual traffic patterns that may indicate exploitation attempts, particularly around the upnp service ports. Organizations should also consider implementing network segmentation to isolate critical systems from potentially vulnerable endpoints, reducing the attack surface and limiting the potential impact of successful exploitation attempts. The vulnerability underscores the importance of maintaining current firmware versions and implementing robust network security practices, particularly for legacy equipment that may not receive regular security updates from manufacturers.