CVE-2026-96891 in DIR-825
Summary
by MITRE • 09/24/2026
A vulnerability was identified in D-Link DIR-825 3.00b32. Affected is the function tunnel_set_params of the file tunnel.c of the component rp-l2tp. The manipulation of the argument peer_hostname leads to out-of-bounds write. The attack may be initiated remotely.
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Analysis
by VulDB Data Team • 09/24/2026
The identified vulnerability in D-Link DIR-825 firmware version 3.00b32 represents a critical security flaw within the Layer Two Tunneling Protocol (L2TP) implementation, specifically located in the tunnel_set_params function of the tunnel.c source file under the rp-l2tp component. This issue is classified as an out-of-bounds write vulnerability, which falls under Common Weakness Enumeration category CWE-787: Out-of-Bounds Write. Such vulnerabilities occur when a program writes data to a memory location outside the bounds of the intended buffer or array, potentially overwriting adjacent memory structures and leading to unpredictable system behavior. In this specific context, the flaw is triggered by the manipulation of the peer_hostname argument passed during the configuration process for L2TP tunnels. The lack of adequate boundary checking allows an attacker to supply a hostname string that exceeds the allocated buffer size, causing data to spill into neighboring memory regions.
The operational impact of this vulnerability is severe due to its remote exploitability. Since the attack can be initiated remotely without requiring prior authentication or physical access to the device, it significantly lowers the barrier for exploitation by malicious actors. An attacker could potentially craft a specially formatted L2TP configuration request that triggers the buffer overflow when processed by the router's firmware. Successful exploitation may lead to arbitrary code execution, allowing the adversary to gain full control over the compromised network infrastructure. This can result in data exfiltration, installation of persistent backdoors, or use of the device as part of a larger botnet for distributed denial-of-service attacks. The integrity and confidentiality of all traffic passing through this router are consequently at risk, undermining the security posture of any connected devices on the local network.
From an offensive security perspective, this vulnerability aligns with MITRE ATT&CK techniques related to initial access and execution via remote services. Specifically, it relates to exploitation for credential dumping or privilege escalation if the compromised process runs with elevated privileges within the embedded Linux environment typical of such routers. The ability to write out-of-bounds often enables attackers to overwrite function pointers or return addresses on the stack, facilitating control flow hijacking. This is a classic precursor to more advanced attacks where the attacker establishes persistence by modifying system binaries or configuration files that survive reboots.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided firmware updates that patch the tunnel_set_params function with proper input validation and bounds checking mechanisms. Administrators should ensure their D-Link DIR-825 devices are running a version of firmware later than 3.00b32, where these issues have been addressed by implementing strict length checks on the peer_hostname parameter before copying it into the destination buffer. In cases where immediate patching is not feasible due to operational constraints or lack of available updates, network-level mitigations should be employed. This includes restricting access to the router's management interface and L2TP services from untrusted networks using firewall rules. Additionally, enabling intrusion detection systems that monitor for anomalous packet sizes in L2TP traffic can help detect attempted exploitation activities. Regular security audits and vulnerability scanning of IoT devices are essential practices to identify such weaknesses before they can be leveraged by adversaries.