CVE-2024-9551 Overview
CVE-2024-9551 is a buffer overflow vulnerability affecting the D-Link DIR-605L router running firmware version 2.13B01 BETA. The flaw resides in the formSetWanL2TP function within /goform/formSetWanL2TP. Attackers can trigger the overflow by manipulating the webpage argument, leading to memory corruption on the affected device. The vulnerability is remotely exploitable and requires low privileges, with no user interaction. A public exploit has been disclosed, increasing the likelihood of opportunistic attacks against exposed devices. The affected DIR-605L model is an end-of-life consumer router still deployed in home and small office environments.
Critical Impact
Remote attackers with low privileges can trigger a buffer overflow in the router's web management interface, potentially achieving code execution or persistent device compromise.
Affected Products
- D-Link DIR-605L Router (hardware)
- D-Link DIR-605L Firmware version 2.13B01 BETA
- Web management interface component /goform/formSetWanL2TP
Discovery Timeline
- 2024-10-06 - CVE-2024-9551 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-9551
Vulnerability Analysis
The vulnerability is a classic buffer overflow [CWE-120] in the L2TP WAN configuration handler of the DIR-605L web interface. The formSetWanL2TP function processes HTTP POST parameters sent to /goform/formSetWanL2TP without validating the length of the supplied webpage argument. When an attacker submits an oversized webpage value, the function copies the user-controlled data into a fixed-size stack buffer, overwriting adjacent memory including saved return addresses.
Successful exploitation can corrupt control flow within the router's HTTP daemon. On MIPS-based embedded devices like the DIR-605L, this typically enables arbitrary code execution as the web server process, which runs with elevated privileges on the device. Attackers can leverage this access to modify configuration, install persistent implants, pivot into internal networks, or enroll the device into a botnet.
Root Cause
The root cause is the absence of bounds checking on the webpage parameter before it is copied into a stack-allocated buffer. The function relies on unsafe string handling routines common in embedded C code, without validating input length against buffer capacity.
Attack Vector
The attack vector is network-based against the router's HTTP administrative interface. An authenticated attacker sends a crafted HTTP POST request to /goform/formSetWanL2TP containing an oversized webpage argument. Because the exploit has been publicly disclosed on GitHub, automated scanning against exposed DIR-605L devices is feasible.
The vulnerability manifests in the L2TP WAN configuration handler. Refer to the GitHub PoC for D-Link Vulnerability for technical details of the input pattern that triggers the overflow.
Detection Methods for CVE-2024-9551
Indicators of Compromise
- HTTP POST requests to /goform/formSetWanL2TP containing abnormally long webpage parameter values.
- Unexpected reboots, crashes, or restarts of the router's web management daemon.
- Outbound connections from the router to unknown hosts, indicating potential post-exploitation implant activity.
- Unauthorized changes to WAN, DNS, or L2TP configuration settings on the DIR-605L.
Detection Strategies
- Monitor network traffic destined for the router's management interface for oversized POST bodies targeting /goform/ endpoints.
- Deploy IDS/IPS signatures matching HTTP requests with webpage parameters exceeding expected length thresholds.
- Correlate router log events with sudden configuration changes or repeated authentication attempts followed by malformed requests.
Monitoring Recommendations
- Log and alert on any external access attempts to the router's administrative interface, which should never be exposed to the internet.
- Track DNS queries from internal clients for signs of DNS hijacking rooted at a compromised router.
- Baseline expected administrative traffic patterns and alert on deviations targeting /goform/formSetWanL2TP.
How to Mitigate CVE-2024-9551
Immediate Actions Required
- Disable remote (WAN-side) management on the DIR-605L to prevent internet-based exploitation.
- Restrict LAN-side access to the web administration interface to trusted management hosts only.
- Change the router's administrative password to a strong unique value to raise the bar for the low-privilege authentication required.
- Plan device replacement, since the DIR-605L is an end-of-life product unlikely to receive vendor patches.
Patch Information
At the time of publication, no official vendor patch has been referenced for CVE-2024-9551. The D-Link DIR-605L is a legacy consumer router. Organizations should consult the D-Link Official Website for end-of-life advisories and consider migrating to a supported model with active security maintenance.
Workarounds
- Segment the affected router behind an upstream firewall that filters administrative traffic and inspects HTTP payload sizes.
- Block inbound WAN access to TCP ports used by the router's HTTP interface (typically 80 and 8080).
- Replace the DIR-605L with a currently supported router model that receives active firmware security updates.
- Where replacement is not immediate, isolate the router on a dedicated management VLAN with strict ACLs limiting who can reach /goform/ endpoints.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
