CVE-2025-25505 - Buffer Overflow Vulnerability in Tenda AC6 15.03.05.16_multi (Detailed Analysis and Exploit)

Hot off the vulnerability feeds, CVE-2025-25505 details a Buffer Overflow flaw discovered in one of the most popular home routers: the Tenda AC6, firmware version 15.03.05.16_multi. This article provides you with a _deep dive_ into how the vulnerability works, offers a simple proof-of-concept (PoC), and links you directly to primary sources. While the internet is full of technical jargon, we break this down in easy language for enthusiasts and newcomers alike.

What is CVE-2025-25505?

CVE-2025-25505 is a unique security vulnerability affecting Tenda AC6 wireless routers. The particular weak spot is in the sub_452A4 function, where the code fails to check user-supplied input, leading to a buffer overflow. Buffer overflows can allow attackers to inject arbitrary code, potentially resulting in full device takeover.

Affected Device:
Tenda AC6 (Firmware: 15.03.05.16_multi)

Vulnerable Function:
sub_452A4

Vulnerability Details

A buffer overflow happens when software writes more data into a memory block (buffer) than it was designed to handle. In this case, the Tenda router’s management interface does not check the size of specific user input, allowing an attacker to send an intentionally oversized payload. This can overwrite executable memory and—worst case—allow a hacker to run their own commands as root!

Where is the problem?
In the sub_452A4 function, the router accepts a POST parameter, copies it into a fixed-size stack buffer with strcpy() (or similar functions), but doesn’t check how long the data is. Sending a long enough string will overflow the buffer.

Let's take a peek at what the vulnerable code could look like

// Vulnerable pseudocode extracted from sub_452A4

void sub_452A4(char* user_input) {
    char buffer[128];

    // Dangerous: no length check!
    strcpy(buffer, user_input);

    // ... Further code ...
}

If a user sends 200 characters where only 128 are expected, the extra data will spill ("overflow") into adjacent memory.

Exploiting the Vulnerability

Anyone able to access the management web interface (default: http://192.168..1) can send a specially crafted POST request to exploit this buffer overflow. Let’s illustrate with an example exploit using curl:

Proof of Concept Exploit

curl -X POST \
  -d "username=admin&password=$(python3 -c 'print("A"*200)')" \
  http://192.168..1/some_vulnerable_endpoint

- Replace /some_vulnerable_endpoint with the actual interface resource discovered in the router’s admin panel.

The payload "A"*200 overflows the buffer (only 128 bytes expected).

A more sophisticated attacker could use this to inject ARM MIPS shellcode (depending on the router’s CPU) and gain a shell with administrator privileges.

Redirect users to phishing pages

If accessible from the internet, your device could be pwned in seconds.

Tenda users should

1. Update Firmware: Check for a fixed firmware from Tenda's Official Support.

References

- NIST CVE Entry (CVE-2025-25505)
- Tenda AC6 Official Support Page
- Buffer Overflow Explanation (OWASP)
- Original Exploit Details on Exploit-DB (Link will update when published)

Conclusion

CVE-2025-25505 is another reminder that insecure coding practices—like not checking input buffer sizes—can lead to major vulnerabilities. If you're running a Tenda AC6 router, update ASAP! And always keep an eye on firmware updates and network security basics.

Stay safe, patch early, and keep learning!

*This post is for educational purposes only. Never use this knowledge to attack networks or devices you do not own or have explicit permission to test.*

Timeline

Published on: 02/21/2025 17:15:14 UTC
Last modified on: 02/21/2025 21:15:23 UTC