CVE-2026-86296 in DIR-822A
Summary
by MITRE • 09/07/2026
A vulnerability was determined in D-Link DIR-822A A_101. This vulnerability affects the function strcpy of the file udhcpcd/serverpacket.c of the component udhcpcd. This manipulation causes stack-based buffer overflow. The attack is possible to be carried out remotely. The exploit has been publicly disclosed and may be utilized.
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Analysis
by VulDB Data Team • 09/07/2026
The D-Link DIR-822A router, specifically firmware version A_101, contains a critical security flaw within its dynamic host configuration protocol client daemon, udhcpcd. This vulnerability stems from the improper handling of input data in the serverpacket.c source file, where the standard C library function strcpy is employed without adequate bounds checking. The strcpy function copies strings from one memory location to another but does not verify if the destination buffer has sufficient space for the incoming data. In this specific implementation, the lack of validation allows an attacker to supply a payload that exceeds the allocated stack size, resulting in a stack-based buffer overflow. This type of flaw is classified under CWE-120, which denotes Buffer Copy without Checking Size of Input, and represents a fundamental failure in input sanitization practices common in embedded systems development where resource constraints often lead developers to prioritize functionality over robust memory management safeguards.
The operational impact of this vulnerability is severe due to its remote exploitability. Since the udhcpcd service typically handles network configuration requests from DHCP servers or rogue devices on the local network, an attacker does not need physical access to the device. By sending a specially crafted packet that triggers the buffer overflow condition, an adversary can overwrite critical data on the stack, including return addresses and saved frame pointers. This manipulation allows for arbitrary code execution with the privileges of the udhcpcd process, which often runs as root or with elevated system permissions in embedded Linux environments. Consequently, successful exploitation grants the attacker full control over the router's operating system, enabling them to pivot into the internal network, intercept sensitive traffic, install persistent malware, or use the compromised device as a node in botnets for distributed denial-of-service attacks.
The fact that an exploit has been publicly disclosed significantly elevates the risk profile of this vulnerability. Publicly available exploits lower the barrier to entry for malicious actors who may lack advanced reverse engineering skills but can leverage existing proof-of-concept code to compromise vulnerable devices at scale. This scenario aligns with tactics observed in the MITRE ATT&CK framework, particularly those involving initial access through exploitation of remote services and privilege escalation via memory corruption techniques. The presence of a known exploit means that automated scanning tools and opportunistic attackers are actively targeting this specific firmware version across the internet, making immediate remediation imperative for any organization or individual still running DIR-822A devices with A_101 firmware.
Mitigation strategies must focus on both immediate containment and long-term resolution. The primary recommendation is to update the router firmware to a patched version released by D-Link that addresses this buffer overflow issue, likely by replacing strcpy with safer alternatives such as strncpy or strlcpy, which enforce length limits during string copying operations. If updating the firmware is not immediately feasible due to hardware limitations or lack of vendor support, network segmentation should be implemented to isolate these devices from critical internal assets. Additionally, deploying intrusion detection systems that can identify anomalous DHCP traffic patterns associated with buffer overflow attempts may provide a layer of defense against exploitation in real-time. Given the age and potential end-of-life status of some D-Link models, replacing outdated hardware with modern routers that adhere to current security standards is also a prudent long-term solution to eliminate this attack vector entirely.