CVE-2024-11237: TP-Link VN020 Buffer Overflow Vulnerability

CVE-2024-11237 Overview

CVE-2024-11237 is a stack-based buffer overflow [CWE-121, CWE-787] affecting the TP-Link VN020-F3v(T) router running firmware version TT_V6.2.1021. The flaw resides in the Dynamic Host Configuration Protocol (DHCP) DISCOVER packet parser, where the hostname argument is processed without proper bounds checking. An unauthenticated attacker on the local network can send a crafted DHCP DISCOVER packet to corrupt the stack and crash the device. A public proof-of-concept exploit is available on GitHub, increasing the risk of opportunistic exploitation against exposed devices.

Critical Impact

Remote attackers can trigger a stack-based buffer overflow in the DHCP DISCOVER handler without authentication or user interaction, leading to denial of service and potential memory corruption on affected TP-Link VN020-F3v(T) routers.

Affected Products

• TP-Link VN020-F3v(T) hardware (all units running the vulnerable firmware)
• TP-Link VN020-F3v(T) firmware version TT_V6.2.1021
• Network segments where the device serves DHCP requests

Discovery Timeline

• 2024-11-15 - CVE-2024-11237 published to the National Vulnerability Database (NVD)
• 2024-11-19 - Last updated in NVD database

Technical Details for CVE-2024-11237

Vulnerability Analysis

The vulnerability lives in the DHCP DISCOVER packet parser of the TP-Link VN020-F3v(T) firmware. When the device receives a DHCP DISCOVER message, it extracts the client hostname option and copies it into a fixed-size stack buffer without validating the supplied length. Because the parser trusts attacker-controlled input from option 12 (Host Name) of the DHCP packet, an oversized value overwrites adjacent stack memory, including saved return addresses and frame pointers.

DHCP DISCOVER traffic is broadcast on UDP port 67 and does not require authentication, prior pairing, or user interaction. Any device on the same broadcast domain as the router can send the malicious packet. The public proof-of-concept hosted at TP-Thumper PoC demonstrates how a crafted hostname option reliably crashes the parser process and renders the router unresponsive.

The Common Weakness Enumeration entries assigned are [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and [CWE-787] (Out-of-bounds Write). EPSS data places the exploitation probability at 4.128% (88.75th percentile), reflecting the availability of working exploit code.

Root Cause

The parser fails to enforce a maximum length on the hostname field before invoking an unsafe memory copy into a stack-allocated buffer. There is no length-check guard, no use of bounded string functions, and no stack canary instrumentation in the affected build, allowing the attacker to fully control the bytes written past the buffer boundary.

Attack Vector

Exploitation occurs over the network adjacent to the device. An attacker connects to the LAN, Wi-Fi network, or any segment reachable by DHCP broadcast traffic. The attacker then transmits a DHCP DISCOVER packet that includes an oversized hostname option. The parser writes the malicious payload past the stack buffer, corrupting control data. The immediate observable outcome is a router crash and loss of network connectivity for downstream clients. Memory corruption on embedded MIPS or ARM targets of this class has historically been used to chain into arbitrary code execution, though only denial of service is confirmed in the public PoC.

A description of the exploitation mechanism and packet structure is documented in the TP-Thumper proof-of-concept source.

Detection Methods for CVE-2024-11237

Indicators of Compromise

• Unexpected reboots, watchdog resets, or unresponsiveness of the TP-Link VN020-F3v(T) router
• DHCP DISCOVER packets on UDP port 67 containing abnormally long option 12 (Host Name) values
• Loss of LAN connectivity coinciding with broadcast DHCP activity from an unknown MAC address
• DHCP clients repeatedly retransmitting DISCOVER messages because the server stopped responding

Detection Strategies

• Inspect DHCP traffic with packet capture tools and alert on option 12 values exceeding typical hostname lengths (RFC 1035 limits hostnames to 255 octets, but legitimate values are usually under 64)
• Deploy network intrusion detection signatures that match malformed DHCP DISCOVER packets targeting embedded gateways
• Correlate router availability monitoring with broadcast DHCP events to identify denial-of-service attempts

Monitoring Recommendations

• Forward DHCP server logs and router crash telemetry to a centralized logging or SIEM platform for anomaly detection
• Track MAC address churn on the LAN and flag previously unseen clients issuing DHCP DISCOVER messages immediately followed by router unavailability
• Maintain an asset inventory of TP-Link VN020-F3v(T) devices and their firmware versions to scope exposure quickly

How to Mitigate CVE-2024-11237

Immediate Actions Required

• Restrict physical and wireless access to the LAN segment serving the affected router to trusted users only
• Disable or replace exposed TP-Link VN020-F3v(T) units in environments where untrusted devices can join the network
• Monitor the TP-Link Official Website for firmware updates addressing the DHCP parser flaw
• Segment guest networks and IoT devices away from production DHCP infrastructure

Patch Information

At the time of NVD publication, no vendor patch was listed for firmware version TT_V6.2.1021. Administrators should track vendor advisories on the TP-Link Official Website and the VulDB entry for this issue for updates. Until a fixed firmware image is released, compensating controls are required.

Workarounds

• Replace affected devices with a router that uses a hardened DHCP implementation if patches are unavailable
• Enforce wired and wireless network access control (802.1X, MAC filtering, WPA3) to prevent untrusted hosts from broadcasting DHCP traffic
• Place the router behind a managed switch capable of DHCP snooping and rate-limiting DHCP DISCOVER messages from untrusted ports
• Apply egress filtering on guest networks so visitor devices cannot reach the management LAN

# Example: enable DHCP snooping on a managed upstream switch (Cisco IOS syntax)
configure terminal
ip dhcp snooping
ip dhcp snooping vlan 10
interface range GigabitEthernet0/1 - 24
 ip dhcp snooping limit rate 10
 no ip dhcp snooping trust
end
write memory