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CVE-2021-39685 is an out-of-bounds write vulnerability in various setup methods of the USB gadget subsystem in the Android kernel. The issue arises due to an incorrect flag check, which allows a local attacker to write outside the bounds of an allocated buffer. This can be exploited for local privilege escalation without requiring additional execution privileges or user interaction.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository contains a proof-of-concept exploit for CVE-2021-39685, a vulnerability in the Linux kernel's USB gadget subsystem (rndis, hid, uac1, uac1_legacy, uac2). The vulnerability allows an attacker to bypass buffer boundaries in USB control request handlers by specifying a wLength greater than the allocated buffer size (4096 bytes), resulting in the ability to read or write up to 65k of kernel memory. The exploit is implemented in a single Python script (gadget.py), which uses pyusb to send crafted USB control transfer requests to a target device. The script is configurable via command-line arguments for vendor/product IDs, function type, direction (read/write), and data length. The README provides detailed background, usage instructions, and references to the relevant kernel patches. The exploit requires a custom build of libusb on the host to allow large control transfer buffers. No network endpoints or external IPs are present; the attack is performed locally via USB. The repository is well-documented and focused solely on demonstrating the vulnerability and its exploitation.
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