Use-after-free in Linux kernel - CVE-2026-63802

Vulnerability identifier: #VU138857

CSH Severity: Low

CVSS v4: 5.7 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63802

CWE-ID: CWE-416

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 use-after-free in __blkcg_rstat_flush() when releasing multiple blkgs in the same blkcg concurrently. A local user can trigger concurrent blkg release operations to cause a denial of service.

The race occurs when one blkg removes another blkg's iostat entries via llist_del_all() while the other blkg is still being processed.

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 6.6.0-145.1.20.157
python3-perf-debuginfo - update to 6.6.0-145.1.20.157
python3-perf - update to 6.6.0-145.1.20.157
perf-debuginfo - update to 6.6.0-145.1.20.157
perf - update to 6.6.0-145.1.20.157
kernel-tools-devel - update to 6.6.0-145.1.20.157
kernel-tools-debuginfo - update to 6.6.0-145.1.20.157
kernel-tools - update to 6.6.0-145.1.20.157
kernel-source - update to 6.6.0-145.1.20.157
kernel-headers - update to 6.6.0-145.1.20.157
kernel-devel - update to 6.6.0-145.1.20.157
kernel-debugsource - update to 6.6.0-145.1.20.157
kernel-debuginfo - update to 6.6.0-145.1.20.157
bpftool-debuginfo - update to 6.6.0-145.1.20.157
kernel - update to 6.6.0-145.1.20.157
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/0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2
• https://git.kernel.org/stable/c/5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6
• https://git.kernel.org/stable/c/96e545410c4f74c89d496c1d5d9ef8d08f14368b
• https://git.kernel.org/stable/c/afebe44facc48a61761e885bbb7f0380d4a603ec
• https://git.kernel.org/stable/c/bbebd9425cad3573d1527441753899b926525a0f

• Use-after-free in Linux kernel block
• openEuler 24.03 LTS SP1 update for kernel
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux
• Ubuntu update for linux-gcp-7.0