CVE-2021-34830 in DAP-1330
Summary
by MITRE • 07/16/2021
This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of D-Link DAP-1330 1.13B01 BETA routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of the Cookie HTTP header. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of the device. Was ZDI-CAN-12028.
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Analysis
by VulDB Data Team • 07/19/2021
The vulnerability identified as CVE-2021-34830 represents a critical buffer overflow flaw in D-Link DAP-1330 1.13B01 BETA routers that exposes devices to remote code execution attacks. This vulnerability falls under the CWE-121 category of stack-based buffer overflow, where insufficient input validation leads to memory corruption. The flaw specifically manifests in the router's web server implementation when processing HTTP Cookie headers, making it particularly dangerous as it requires no authentication for exploitation. Network-adjacent attackers can leverage this weakness to gain full control over affected devices, potentially compromising entire networks through lateral movement.
The technical root cause of this vulnerability stems from improper bounds checking within the HTTP header processing routine. When the router receives an HTTP request containing a Cookie header, the system fails to validate the length of the incoming data before copying it into a predetermined stack-based buffer. This classic buffer overflow condition occurs because the application assumes that user-supplied data will not exceed a certain size, but does not enforce this limitation through proper input validation. The lack of length validation creates a scenario where maliciously crafted cookie values can overwrite adjacent memory locations, potentially corrupting the program's execution flow and allowing attackers to inject and execute arbitrary code.
The operational impact of this vulnerability extends beyond simple device compromise, as it enables attackers to establish persistent access to network infrastructure. Once exploited, the attacker gains execution context with the privileges of the router's web server process, which typically operates with elevated permissions. This allows for complete network takeover including DNS hijacking, traffic interception, and potential lateral movement to other network segments. The vulnerability's accessibility without authentication makes it particularly attractive to threat actors, as it eliminates the need for credential harvesting or other preliminary attack steps. Organizations using D-Link DAP-1330 routers are at significant risk, as the attack surface includes all devices accessible to network-adjacent attackers, potentially including internal network segments.
Mitigation strategies for this vulnerability should prioritize immediate firmware updates from D-Link to address the buffer overflow condition. Organizations should also implement network segmentation and access controls to limit the attack surface of affected devices. The ATT&CK framework categorizes this vulnerability under T1059.007 for command and scripting interpreter and T1071.004 for application layer protocol, highlighting the need for network monitoring and intrusion detection systems. Additional protective measures include implementing web application firewalls to filter malicious cookie headers, disabling unnecessary services, and conducting regular vulnerability assessments. Given the nature of the flaw, organizations should also consider network-wide scanning for other potentially vulnerable D-Link devices and implement proper network access controls to prevent unauthorized access to sensitive network infrastructure.