CVE-2026-63902 USB: serial: cypress_m8: validate interrupt packet headers
A local attacker with physical access can trigger an out-of-bounds read in the Cypress M8 USB serial driver, potentially causing a system crash or code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-63902?
CVE-2026-63902 is a memory corruption vulnerability in Linux, published on 19 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
In the Linux kernel, the following vulnerability has been resolved:
USB: serial: cypress_m8: validate interrupt packet headers
cypress_read_int_callback() parses the interrupt-in buffer according to the selected Cypress packet format. Format 1 has a two-byte status/count header and format 2 has a one-byte combined status/count header. The usb-serial core sizes the interrupt-in buffer from the endpoint descriptor's wMaxPacketSize, and successful interrupt transfers can complete short when URB_SHORT_NOT_OK is not set.
Check that the completed packet contains the selected header before reading it. Malformed short reports are ignored and the interrupt URB is resubmitted through the existing retry path, preventing out-of-bounds header-byte reads.
KASAN report as below: KASAN slab-out-of-bounds in cypress_read_int_callback+0x240/0x7f0 Read of size 1 Call trace: cypress_read_int_callback() (drivers/usb/serial/cypress_m8.c:1009) __usb_hcd_giveback_urb() dummy_timer()
[ johan: use constants in header length sanity checks ]
Which versions are affected by CVE-2026-63902?
How do I fix CVE-2026-63902?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-63902 being exploited?
There is no known exploitation of CVE-2026-63902 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-63902, DEBIAN-CVE-2026-63902, GHSA-28gg-7x4r-8gcw, ROOT-OS-UBUNTU-2204-CVE-2026-63902, UBUNTU-CVE-2026-63902.