What is Type Confusion?
A type confusion vulnerability occurs when a program incorrectly treats a piece of data as a different type than intended. This can lead to memory corruption, allowing an attacker to manipulate the execution flow of a program, potentially leading to arbitrary code execution (ACE).

Where is the Vulnerability?
- The flaw has been identified in the PostScript interpreter used in various Lexmark devices (such as printers and multi-function devices).
- PostScript is a page description language used for rendering documents on printers. It is Turing-complete, meaning it can execute complex operations, making it a potential target for exploitation.
How Can an Attacker Exploit This?
- Crafting a Malicious PostScript File:
- The attacker creates a maliciously crafted PostScript document with type confusion triggers.
- This could involve tricking the interpreter into misinterpreting memory values, leading to unintended behavior.
- Executing Arbitrary Code:
- The misinterpretation of data types could allow an attacker to overwrite memory, hijack function pointers, or execute injected shellcode.
- Since Lexmark devices often run with elevated privileges, this could give the attacker full control over the device.
- Delivery Methods:
- The attacker could exploit this vulnerability by:
- Sending a malicious print job over the network.
- Tricking a user into printing a compromised document.
- Exploiting remote printing features if the printer is exposed to the internet.
- The attacker could exploit this vulnerability by:
Potential Impact
- Remote Code Execution (RCE): The attacker could gain full control over the printer or embedded system.
- Network Pivoting: If the printer is inside a corporate network, it could be used as an entry point for further attacks.
- Data Exfiltration: Malicious scripts could intercept sensitive documents sent to the printer.
- Denial of Service (DoS): The attacker could crash or disrupt the device’s functionality.
Mitigation Strategies
- Firmware Updates:
- Lexmark has likely released patches for affected devices. Users should update their firmware immediately.
- Disable Unnecessary Features:
- If PostScript printing is not required, disable it in the device settings.
- Network Security Measures:
- Restrict printer access to trusted networks only.
- Use firewalls to block untrusted connections.
- Monitor Print Logs:
- Regularly check for unusual printing activity, such as unknown users submitting jobs.
Conclusion
This type confusion vulnerability in Lexmark’s PostScript interpreter presents a serious security risk, potentially leading to remote code execution. Organizations should apply patches, restrict printer access, and monitor activity to mitigate the threat.