CVE-2021-29295 in DSP-W215
Summary
by MITRE • 08/11/2021
** UNSUPPORTED WHEN ASSIGNED **Null Pointer Dereference vulnerability exists in D-Link DSP-W215 1.10, which could let a remote malicious user cause a denial of servie via usr/bin/lighttpd. It could be triggered by sending an HTTP request without URL in the start line directly to the device. NOTE: The DSP-W215 and all hardware revisions is considered End of Life and as such this issue will not be patched.
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Analysis
by VulDB Data Team • 08/04/2024
The CVE-2021-29295 vulnerability represents a critical null pointer dereference flaw discovered in D-Link DSP-W215 wireless router firmware version 1.10. This device operates under the End of Life status, indicating that D-Link has ceased support and patch development for this hardware revision. The vulnerability resides within the lighttpd web server component located at usr/bin/lighttpd, which serves as the primary HTTP server interface for the device's web management portal. The flaw manifests when the web server processes malformed HTTP requests that lack a URL in the request start line, creating a condition where the application attempts to dereference a null pointer during request handling. This type of vulnerability falls under CWE-476, which specifically addresses null pointer dereference conditions that can lead to application crashes or system instability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable more sophisticated attack vectors despite the device's end-of-life status. Remote attackers can exploit this weakness by crafting specially formatted HTTP requests that bypass normal URL parsing mechanisms within the lighttpd server. When such a malformed request reaches the device, the web server process crashes due to the null pointer dereference, resulting in a complete denial of service condition that renders the router's management interface inaccessible. This disruption affects both the web-based administrative interface and potentially the device's network connectivity if the web server failure impacts core routing functionality. The vulnerability demonstrates poor input validation practices where the application fails to properly sanitize HTTP request headers before processing them, creating an execution path that leads to memory access violations.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through exploitation of application-level flaws. The attack surface is particularly concerning given that the vulnerability can be triggered over the network without requiring authentication, making it a prime candidate for automated scanning and exploitation by threat actors. The fact that this device is end-of-life means that organizations may not have access to official patches or updates, forcing them to rely on network segmentation, firewall rules, or physical security measures to mitigate exposure. Security professionals should note that while D-Link has indicated no further patches will be developed for this device, the vulnerability represents a classic example of how legacy network equipment can present ongoing security risks in enterprise environments where such devices may still be operational. Organizations should consider immediate remediation actions including network isolation, replacement of affected devices, or implementation of network-based intrusion detection systems to monitor for exploitation attempts targeting this specific vulnerability. The broader implications highlight the importance of maintaining inventory control over legacy network infrastructure and establishing clear retirement policies for end-of-life devices to prevent such vulnerabilities from remaining unpatched in production environments.