Out-of-bounds write in Linux kernel - CVE-2026-63825

Vulnerability identifier: #VU138832

CSH Severity: Low

CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63825

CWE-ID: CWE-787

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to an out-of-bounds write in inflate_fast() when processing IP payload compression data concurrently on multiple cpus. A local user can trigger concurrent execution of the vulnerable code path to cause a denial of service.

The issue occurs because global gcov counters can change between multiple loads during execution, producing inconsistent loop values.

Linux kernel
openEuler
Ubuntu
bpftool
python3-perf-debuginfo
python3-perf
perf-debuginfo
perf
kernel-tools-devel
kernel-tools-debuginfo
kernel-tools
kernel-source
kernel-headers
kernel-devel
kernel-debugsource
kernel-debuginfo
bpftool-debuginfo
kernel
linux (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
bpftool - update to 5.10.0-327.0.0.228
python3-perf-debuginfo - update to 5.10.0-327.0.0.228
python3-perf - update to 5.10.0-327.0.0.228
perf-debuginfo - update to 5.10.0-327.0.0.228
perf - update to 5.10.0-327.0.0.228
kernel-tools-devel - update to 5.10.0-327.0.0.228
kernel-tools-debuginfo - update to 5.10.0-327.0.0.228
kernel-tools - update to 5.10.0-327.0.0.228
kernel-source - update to 5.10.0-327.0.0.228
kernel-headers - update to 5.10.0-327.0.0.228
kernel-devel - update to 5.10.0-327.0.0.228
kernel-debugsource - update to 5.10.0-327.0.0.228
kernel-debuginfo - update to 5.10.0-327.0.0.228
bpftool-debuginfo - update to 5.10.0-327.0.0.228
kernel - update to 5.10.0-327.0.0.228
linux (Ubuntu package) - addressed in versions 7.0.0-31.31, 7.0.0-31.31.1, 7.0.0-31.31~24.04.1, 7.0.0-1006.7, 7.0.0-1011.11~24.04.1, 7.0.0-1012.12, 7.0.0-1012.12~24.04.1
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1013.13

• https://git.kernel.org/stable/c/49d893b9cbcfc5802a32e53a64c6c6956670d65b
• https://git.kernel.org/stable/c/56cb9b7d96b28a1173a510ab25354b6599ad3a33
• https://git.kernel.org/stable/c/5b959c1dbb4522b9e3ac4e26ad638b8784869841

• Out-of-bounds write in Linux kernel inflate_fast()
• openEuler 22.03 LTS SP4 update for kernel
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux
• Ubuntu update for linux-gcp-7.0