CVE-2021-26709 in DSL-320B-D1
Summary
by MITRE • 04/07/2021
** UNSUPPORTED WHEN ASSIGNED ** D-Link DSL-320B-D1 devices through EU_1.25 are prone to multiple Stack-Based Buffer Overflows that allow unauthenticated remote attackers to take over a device via the login.xgi user and pass parameters. NOTE: This vulnerability only affects products that are no longer supported by the maintainer.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/03/2024
The CVE-2021-26709 vulnerability affects D-Link DSL-320B-D1 devices running firmware versions up to EU_1.25, representing a critical stack-based buffer overflow issue that compromises device security. This vulnerability resides in the web interface handling of authentication parameters, specifically within the login.xgi script that processes user and password inputs. The flaw occurs when the device fails to properly validate input length before copying data to fixed-size stack buffers, creating a condition where maliciously crafted input can overwrite adjacent memory locations. According to CWE-121, this represents a classic stack-based buffer overflow vulnerability that allows attackers to execute arbitrary code or cause system crashes. The vulnerability is particularly concerning as it affects devices that are no longer supported by D-Link, meaning users cannot receive official security patches or updates to address the issue.
The technical implementation of this vulnerability involves the device's web server processing user authentication requests through the login.xgi endpoint. When unauthenticated attackers send specially crafted HTTP requests containing overly long username or password parameters, the device's input handling code fails to perform adequate bounds checking before copying the data into stack buffers. This allows attackers to overwrite return addresses and other critical stack data, potentially enabling remote code execution. The attack surface is further expanded by the fact that the vulnerability is accessible without authentication requirements, making it particularly dangerous for networked devices. The ATT&CK framework categorizes this as a privilege escalation technique through code injection, specifically targeting the device's web interface as an entry point for lateral movement and system compromise.
The operational impact of CVE-2021-26709 extends beyond simple device compromise, as attackers can gain full administrative control over affected D-Link DSL-320B-D1 devices. Once exploited, malicious actors can modify device configuration settings, install persistent backdoors, or redirect network traffic through the compromised router. The vulnerability's remote nature means that attackers do not require physical access or network credentials to exploit the flaw, making it particularly attractive for large-scale attacks against unpatched networks. Given that these devices are legacy products no longer receiving security updates, organizations using them face significant risk of persistent compromise, especially in environments where network infrastructure devices are not regularly audited for security vulnerabilities.
Mitigation strategies for CVE-2021-26709 are limited due to the end-of-life status of the affected devices, but several defensive measures can reduce exposure risk. Network segmentation should be implemented to isolate affected devices from critical network segments, while strict firewall rules can limit access to the web interface and related ports. Organizations should consider replacing affected DSL-320B-D1 devices with supported models that receive regular security updates and patches. Network monitoring solutions should be configured to detect unusual traffic patterns or attempts to access the login.xgi endpoint with malformed parameters. Additionally, implementing network access control lists and disabling unnecessary services can reduce the attack surface for these vulnerable devices. The lack of official patches for this vulnerability underscores the importance of maintaining up-to-date security practices and avoiding deployment of unsupported network infrastructure equipment.