CVE-2024-49849 - Siemens TIA Portal Products Log File Parsing RCE Explained

A new critical vulnerability, CVE-2024-49849, has been discovered affecting a large range of Siemens’ industrial automation products, including their TIA Portal suite. This post breaks down the vulnerability in simple terms, shows how it might be exploited, and gives you all the essential references you need. If you develop, integrate, or secure industrial control systems using Siemens products, this is a must-read.

In Plain English: What is CVE-2024-49849?

CVE-2024-49849 is a _type confusion vulnerability_ found in the way certain Siemens software products parse log files. A type confusion occurs when code assumes a variable is of one data type but it’s actually of another. When that happens, an attacker can take control of program execution—potentially running any code they want with the application’s privileges.

SIMATIC STEP 7 (V16–V19)

- SIMATIC WinCC Unified / WinCC (V16–V19)

SINAMICS Startdrive (V16–V19)

- SIRIUS Safety ES / Soft Starter ES (V17–V19)

The Bad Log File

The weakness lies in how these Siemens applications open and process log files. Attackers can craft a _malicious log file_—something that may look like regular log output but contains special insertions meant to confuse the program’s data handling.

Practical Exploitation Scenario

1. Initial Access: Attacker gets a malicious log file onto a victim’s workstation—via email, supply chain compromise, social engineering (“Open this error log, please!”), or maybe malware.
2. Trigger the Vulnerability: Victim opens the tainted log file using a vulnerable Siemens application.
3. Type Confusion: Because the application doesn’t check the log file’s contents properly, it misinterprets data types inside the file.
4. Remote Code Execution: The attacker’s payload gets executed with the same rights as the application—often high-privileged.

Simple Code Snippet Example

The real bug is buried in Siemens’ closed-source binary code, but to illustrate, here’s a simplified Python example:

# The application expects each log entry to be an integer, but no type check is enforced.
def parse_log_entry(entry):
    # Dangerous: Directly using eval on data from the log file!
    return eval(entry)

# Attacker's crafted log entry
malicious_entry = "__import__('os').system('calc.exe')"  # On Windows, opens Calculator

# This would get executed during log parsing:
parse_log_entry(malicious_entry)

In a real Siemens app, the type confusion might let a log entry be treated as something else entirely, letting the attacker break free from data parsing and trigger code execution.

Possible Exploit Path

While proof-of-concept code is (as of June 2024) not public, based on how log file parsing mistakes have been weaponized in the past, here’s a basic outline:

Craft a log file (“attack.log”) with data that, under weak parsing, causes a type confusion.

2. Embed payload that, when the variable is wrongly interpreted, gets run as legitimate code or redirected to a system shell.

Send to target, who opens it with their Siemens tool.

4. Payload executes with user privileges—possibly escalating to SYSTEM or root in some situations.

Minimal Exploit Example *(Hypothetical)*

The following pseudo-C attack illustrates the style of bug (“type confusion” due to lack of input checking):

// PSEUDO-C (illustrative, NOT Siemens code)

typedef struct {
    int type;
    union {
        int asInt;
        char asStr[256];
    } data;
} LogEntry;

void parseEntry(LogEntry *entry) {
    if (entry->type == 1) {
        // expects integer, but data could be string
        processInteger(entry->data.asInt);
        // If 'data' actually holds attacker-built string, weird stuff happens
    }
}

If an attacker fakes ‘type’ but actually stores a string, the app may treat pointer data as an integer and let unchecked code run wild.

Siemens Advisory and Official References

- Siemens Security Advisory: SSA-264624: Multiple SIMATIC and Related Products Vulnerable to Log File Parsing Flaw (CVE-2024-49849)
- CVE Details: NVD Listing for CVE-2024-49849

*(If links change, find details via Siemens ProductCERT portal or official CVE databases.)*

What Should You Do?

1. Don’t Open Untrusted Log Files — EVER. Avoid opening logs you didn’t generate yourself, especially from email, USB, or network shares.

Limit Access & Rights. Run TIA Portal apps with the least privileges needed.

4. Network Segmentation. Limit who and what can access Windows desktops with Siemens software installed.
5. Monitor for Suspicious Activity. Watch for odd behavior around log files and application launches.

Conclusion

The CVE-2024-49849 flaw is a sober reminder: even “safe” log file parsing can be deadly if input isn’t validated. If you work with Siemens’ automation suite, assume log files are dangerous until fixed—and patch as soon as updates become available.

For More, See

- Siemens ProductCERT
- NVD: CVE-2024-49849

Stay safe! If you have questions, comment below or hit us on Twitter.


*Disclosure: This post is independent and is not affiliated with Siemens or any vendor.*

Timeline

Published on: 12/10/2024 14:30:44 UTC