CVE-2024-8946 in MicroPython
Summary
by MITRE • 09/17/2024
A vulnerability was found in MicroPython 1.23.0. It has been classified as critical. Affected is the function mp_vfs_umount of the file extmod/vfs.c of the component VFS Unmount Handler. The manipulation leads to heap-based buffer overflow. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. The name of the patch is 29943546343c92334e8518695a11fc0e2ceea68b. It is recommended to apply a patch to fix this issue. In the VFS unmount process, the comparison between the mounted path string and the unmount requested string is based solely on the length of the unmount string, which can lead to a heap buffer overflow read.
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Analysis
by VulDB Data Team • 05/02/2025
The vulnerability identified as CVE-2024-8946 represents a critical heap-based buffer overflow in MicroPython version 1.23.0, specifically within the Virtual File System (VFS) unmount handler functionality. This flaw resides in the mp_vfs_umount function located in the extmod/vfs.c file, making it a core component of the operating system's file management infrastructure. The vulnerability stems from an insufficient validation mechanism during the unmount process where the system only compares the length of the mounted path string against the unmount request string without proper string content verification, creating a fundamental security gap that can be exploited through remote attack vectors.
The technical implementation of this vulnerability exploits a classic buffer overflow condition by bypassing proper string boundary checks during VFS operations. When a user or attacker requests to unmount a filesystem, the system performs a length-based comparison rather than a comprehensive string equality check, allowing malicious input to exceed allocated buffer boundaries. This heap-based overflow creates opportunities for arbitrary code execution, memory corruption, and potential privilege escalation within the MicroPython runtime environment. The vulnerability's classification as critical reflects its potential to enable remote code execution and system compromise, particularly given that public exploitation techniques have been documented and disseminated.
The operational impact of CVE-2024-8946 extends beyond simple denial of service scenarios to encompass full system compromise capabilities. Attackers can leverage this vulnerability to execute malicious code within the MicroPython environment, potentially gaining access to sensitive data, compromising device integrity, or using the compromised system as a pivot point for further attacks. The remote exploitability means that systems running affected MicroPython versions are immediately at risk without proper patching or mitigation measures. This vulnerability directly maps to CWE-121 heap-based buffer overflow and aligns with ATT&CK techniques related to privilege escalation and code execution through software vulnerabilities.
Security remediation for this vulnerability requires immediate application of the official patch identified by the commit hash 29943546343c92334e8518695a11fc0e2ceea68b. Organizations should conduct comprehensive vulnerability assessments of all systems running MicroPython 1.23.0 to identify exposed devices and implement proper network segmentation to limit potential attack surfaces. Additionally, system administrators should monitor for any signs of exploitation attempts and consider implementing runtime monitoring solutions to detect anomalous behavior patterns associated with buffer overflow exploitation attempts. The patch addresses the root cause by implementing proper string comparison mechanisms that validate both length and content during VFS unmount operations, ensuring that buffer boundaries are properly respected during all file system manipulation activities.