Source URL: https://www.truesec.com/hub/blog/attacking-powershell-clixml-deserialization
Source: Hacker News
Title: Attacking PowerShell Clixml Deserialization
Feedly Summary: Comments
AI Summary and Description: Yes
**Summary:**
The text details a series of research findings related to security vulnerabilities associated with PowerShell’s CLIXML deserialization mechanism. Specifically, it highlights the risks stemming from the serialization and deserialization processes in PowerShell, emphasizing how these mechanisms can be exploited to achieve Remote Code Execution (RCE) or other malicious actions if untrusted data is deserialized. The article also outlines various attack vectors and mitigation strategies, presenting valuable insights for security professionals focused on secure PowerShell development and operational practices.
**Detailed Description:**
The article discusses significant security vulnerabilities related to PowerShell, specifically through CLIXML deserialization attacks. Here are the major points covered:
– **Research Background:**
– The author submitted findings to Microsoft Security Response Center (MSRC) regarding vulnerabilities in the deserialization process, which the MSRC later acknowledged as “fixed.” However, risks remain as the underlying vulnerabilities can still be exploited.
– **Deserialization Attacks:**
– Deserialization is the process of reconstructing an object from a serialized format. While typically safe, if a program deserializes untrusted data, it may allow attackers to execute malicious code.
– The specific vulnerability discussed is CWE-502 (Deserialization of Untrusted Data).
– **Gadget Chains:**
– The text defines a “gadget chain” as a sequence of function calls triggered by deserializing malicious data, ultimately leading to security impacts such as RCE or information leakage.
– Various examples of gadgets are explored, showing how they can be exploited in PowerShell environments.
– **Attack Vectors:**
– The document elaborates on different scenarios where these vulnerabilities can be leveraged, including:
– **PowerShell Remoting:** How an attacker could compromise a server and execute CLIXML deserialization attacks against an unsuspecting client connecting to it.
– **Hyper-V Guest-to-Host Breakout:** The potential for guest systems to exploit deserialization vulnerabilities to escape their containment environment.
– **Mitigation Strategies:**
– Developing secure PowerShell modules to avoid introducing new vulnerabilities.
– Recommendations for IT operations to minimize risk, such as regularly reviewing loaded PowerShell modules, reducing their count, and utilizing dedicated workstations for administrative tasks.
– Importance of avoiding property names like “Action” which can lead to critical vulnerabilities.
– **Disclosure Timeline and Community Response:**
– A timeline of disclosure events highlights the interactions between the researcher and Microsoft regarding the identified vulnerabilities and subsequent actions taken by both parties.
**Key Practical Implications:**
– Security professionals must be aware of the risks associated with PowerShell and the specifics of handling deserialized data. This includes rigorous testing and validation of user-defined types, converters, and format files used within PowerShell scripts and modules.
– Implementing strict development practices that account for deserialization vulnerabilities is critical.
– Continuous education concerning the evolving security landscape of scripting languages and ensuring compliance with security best practices can significantly mitigate the associated risks.