CVE-2023-42801 in moonlight-common-c
Summary
by MITRE • 12/14/2023
Moonlight-common-c contains the core GameStream client code shared between Moonlight clients. Moonlight-common-c is vulnerable to buffer overflow starting in commit f57bd745b4cbed577ea654fad4701bea4d38b44c. A malicious game streaming server could exploit a buffer overflow vulnerability to crash a moonlight client. Achieving RCE is possible but unlikely, due to stack canaries in use by modern compiler toolchains. The published binaries for official clients Qt, Android, iOS/tvOS, and Embedded are built with stack canaries, but some unofficial clients may not use stack canaries. This vulnerability takes place after the pairing process, so it requires the client to be tricked into pairing to a malicious host. It is not possible to perform using a man-in-the-middle due to public key pinning that takes place during the pairing process. The bug was addressed in commit b2497a3918a6d79808d9fd0c04734786e70d5954.
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Analysis
by VulDB Data Team • 12/14/2023
The vulnerability identified as CVE-2023-42801 affects moonlight-common-c, a critical component that serves as the core GameStream client code shared across various Moonlight client implementations. This library forms the foundation for streaming gaming content from remote servers to client devices, making it a prime target for exploitation within the gaming streaming ecosystem. The buffer overflow vulnerability manifests in the codebase starting from commit f57bd745b4cbed577ea654fad4701bea4d38b44c, representing a significant security weakness that could compromise client systems during the game streaming process. The affected library operates within the broader context of networked gaming services where client-server communication must maintain both security and reliability standards.
Technical exploitation of this buffer overflow vulnerability occurs during the post-pairing phase of the GameStream protocol, requiring specific conditions to be met for successful exploitation. The attack vector necessitates that the client be tricked into pairing with a malicious host, which represents a social engineering component that adds complexity to the attack scenario. The vulnerability specifically targets memory management flaws that allow an attacker to write beyond allocated buffer boundaries, potentially causing memory corruption that leads to application crashes. While the vulnerability does not directly enable remote code execution through simple network manipulation, the potential for achieving RCE remains theoretically possible but unlikely due to modern compiler protections such as stack canaries that are employed in official client builds. The implementation of stack canaries represents a standard security mitigation technique that helps detect stack buffer overflows before they can be exploited for code execution.
The operational impact of this vulnerability extends beyond simple client crashes to potentially compromise the entire gaming streaming experience and user security posture. When a malicious server successfully exploits this buffer overflow, it can cause the client application to terminate unexpectedly, disrupting the gaming session and potentially exposing users to further security risks. The requirement for prior pairing with a malicious host creates a specific attack window that limits exploitation but does not eliminate it entirely, as users may be deceived into connecting to compromised servers. This vulnerability demonstrates the importance of secure coding practices in networked applications, particularly those handling sensitive user interactions and data transmission. The fact that official client binaries are built with stack canaries while unofficial implementations may lack these protections highlights the critical need for consistent security practices across all software distributions.
Mitigation strategies for this vulnerability focus on both immediate remediation and long-term security improvements within the Moonlight ecosystem. The vulnerability was addressed through commit b2497a3918a6d79808d9fd0c04734786e70d5954 which implemented proper buffer boundary checks and memory management safeguards. Users should ensure their Moonlight clients are updated to versions that include this fix, particularly since the vulnerability requires a specific attack scenario involving user interaction during the pairing process. Security practitioners should monitor for unofficial client implementations that may not include the necessary protections and advise users accordingly. The vulnerability also underscores the importance of public key pinning mechanisms that prevent man-in-the-middle attacks, as this security feature effectively blocks certain exploit vectors while requiring additional protections for the pairing process itself. This case study aligns with common CWE categories related to buffer overflows and improper input validation, demonstrating how seemingly minor memory management issues can create significant security implications in networked applications. Organizations should consider implementing additional monitoring for client-server communications and user pairing activities as part of their overall security posture to detect and prevent similar vulnerabilities in other streaming and gaming applications.