Improper input validation in Linux kernel - CVE-2026-63956

Vulnerability identifier: #VU138693

CSH Severity: Medium

CVSS v4: 5.2 [CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63956

CWE-ID: CWE-20

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows an attacker with physical access to cause a denial of service or corrupt memory.

The vulnerability exists due to improper input validation in the cypress_m8 USB serial driver when processing a malicious USB device with a too-small interrupt-out endpoint max packet size. An attacker with physical access can connect a specially crafted USB device to cause a denial of service or corrupt memory.

The issue can be triggered if a device reports an interrupt-out endpoint max packet size smaller than eight bytes.

Linux kernel
openEuler
Ubuntu
kernel-debugsource
python3-perf-debuginfo
python3-perf
perf-debuginfo
perf
kernel-tools-devel
kernel-tools-debuginfo
kernel-tools
kernel-source
kernel-headers
kernel-devel
kernel-debuginfo
bpftool-debuginfo
bpftool
kernel
kernel-extra-modules
linux-ibm (Ubuntu package)
linux-aws (Ubuntu package)
linux-azure (Ubuntu package)
linux-nvidia (Ubuntu package)
linux-nvidia-bos (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
kernel-debugsource - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
python3-perf-debuginfo - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
python3-perf - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
perf-debuginfo - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
perf - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-tools-devel - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-tools-debuginfo - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-tools - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-source - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-headers - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-devel - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-debuginfo - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
bpftool-debuginfo - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
bpftool - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel - addressed in versions 5.10.0-327.0.0.228, 6.6.0-145.3.29.160
kernel-extra-modules - update to 6.6.0-145.3.29.160
linux-ibm (Ubuntu package) - addressed in versions 7.0.0-1008.8, 7.0.0-1010.10
linux-aws (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1015.15
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1009.9, 7.0.0-1010.10
linux-nvidia (Ubuntu package) - addressed in versions 7.0.0-1016.16, 7.0.0-1016.16~24.04.1
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2016.16

• https://git.kernel.org/stable/c/1ef25704bd3b625fd151c09feee459479f71ee64
• https://git.kernel.org/stable/c/284105c40fc31fff90cdab8a0377aaeb92f87f0e
• https://git.kernel.org/stable/c/4bcaa59f403dbde6328604a500d65ee8d40975d9
• https://git.kernel.org/stable/c/4fcb22218f0a7229b7ce3b3952fb644def293fa5
• https://git.kernel.org/stable/c/52e18ae0c47c5c89e18fcd8022f287f7cc8802ec
• https://git.kernel.org/stable/c/6c13f3bb652bc8665e709ba07122612586aea648
• https://git.kernel.org/stable/c/ad3d1628a46134276546d7a12fedf04be9979158
• https://git.kernel.org/stable/c/e1a9d791fd66ab2431b9e6f6f835823809869047

• Improper input validation in Linux kernel usb serial driver
• Ubuntu update for linux-ibm
• Ubuntu update for linux-azure
• Ubuntu update for linux-aws
• openEuler 22.03 LTS SP4 update for kernel
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia
• openEuler 24.03 LTS SP3 update for kernel