Listen to this Post
A critical stack-based buffer overflow vulnerability, identified as CVE-2026-3768, exists in the Tenda F453 router running firmware version 1.0.0.3. The flaw is located within the `formWrlExtraSet` function, which is accessible via the `/goform/WrlExtraSet` endpoint. The vulnerability is triggered by manipulating the `GO` argument in an HTTP request. When the `formWrlExtraSet` function handles this parameter, it passes the user-supplied input to the `sub_3A7D8` function. Inside this function, the `sprintf` routine copies the content of the `GO` argument into a stack-based buffer (s_) without performing any bounds checking or length validation. Because there is no restriction on the size of the input, an attacker can send an extremely long string for the `GO` parameter. This oversized data overflows the allocated buffer on the stack, overwriting adjacent memory regions such as return addresses and function pointers. This memory corruption can lead to a denial of service by crashing the device, or it can be leveraged to achieve remote code execution with the privileges of the `httpd` process. The attack requires no user interaction and can be initiated remotely over the network. A proof-of-concept exploit has been publicly released, increasing the risk of widespread exploitation .
Platform: Tenda F453
Version: 1.0.0.3
Vulnerability: Stack Buffer Overflow
Severity: High (CVSS 8.8)
Date: March 8, 2026
Prediction: Patch expected May 2026
What Undercode Say:
Analysis
CVE-2026-3768 is a serious threat to Tenda F453 devices due to the public availability of exploit code and the low complexity of the attack. The vulnerability is in the `httpd` web server, which is typically exposed to local networks and often to the internet if remote management is enabled. Successful exploitation grants an attacker full control over the router, allowing them to monitor traffic, pivot to internal networks, or add the device to a botnet.
Exploit
The following is a proof-of-concept HTTP request that demonstrates how to trigger the buffer overflow:
POST /goform/WrlExtraSet HTTP/1.1 Host: 192.168.0.1 User-Agent: Mozilla/5.0 Accept: / Accept-Language: en Content-Type: application/x-www-form-urlencoded Content-Length: 1200 GO=$(python -c 'print "A" 1000 + "\xXX\xXX\xXX\xXX"')
A more precise exploit would use a debugging tool to calculate the exact offset to control the return address:
Generate a cyclic pattern to find the offset /usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l 1200 Use the pattern in the GO parameter and analyze the crash in a debugger to find the EIP offset /usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -q 0xXXXXXXXX
Protection from this CVE
- Firewall Rules: Block external access to ports 80 and 443 (or the router’s management port) from the WAN interface.
- Disable Features: Turn off remote management if it is not strictly necessary.
- Network Segmentation: Place the router in a segmented network to limit the impact of a compromise.
- Monitoring: Monitor logs for requests to `/goform/WrlExtraSet` with excessively long `GO` parameters.
- Vendor Update: Regularly check Tenda’s official website for a patched firmware version .
Impact
Confidentiality: An attacker can dump the firmware, extract credentials, and sniff network traffic .
Integrity: The device configuration can be altered, and malicious firmware can be flashed .
Availability: The router can be crashed repeatedly, leading to a permanent denial of service .
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
