Bug 2502357 (CVE-2026-63902)

Summary: CVE-2026-63902 kernel: USB: serial: cypress_m8: validate interrupt packet headers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's `cypress_m8` USB serial driver. This vulnerability allows a local attacker to cause a denial of service (DoS) due to an out-of-bounds read. The `cypress_read_int_callback()` function does not properly validate the length of interrupt packets, leading to attempts to read beyond allocated memory when processing malformed short reports. This can result in system instability.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-07-19 16:03:45 UTC 
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 ]
Comment 1 Keith Grant 2026-07-21 20:48:02 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071944-CVE-2026-63902-68cb@gregkh/T