Out-of-bounds read in Linux kernel - CVE-2026-63796

Vulnerability identifier: #VU138851

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-2026-63796

CWE-ID: CWE-125

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 read in the ocfs2 group descriptor bitmap handling in fs/ocfs2/suballoc.c when processing a crafted group bitmap descriptor. A local user can provide a descriptor with oversized bg_size or bg_bits values to cause a denial of service.

Exploitation requires access to a malicious ocfs2 filesystem image or on-disk metadata.

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 5.10.0-328.0.0.229
python3-perf-debuginfo - update to 5.10.0-328.0.0.229
python3-perf - update to 5.10.0-328.0.0.229
perf-debuginfo - update to 5.10.0-328.0.0.229
perf - update to 5.10.0-328.0.0.229
kernel-tools-devel - update to 5.10.0-328.0.0.229
kernel-tools-debuginfo - update to 5.10.0-328.0.0.229
kernel-tools - update to 5.10.0-328.0.0.229
kernel-source - update to 5.10.0-328.0.0.229
kernel-headers - update to 5.10.0-328.0.0.229
kernel-devel - update to 5.10.0-328.0.0.229
kernel-debugsource - update to 5.10.0-328.0.0.229
kernel-debuginfo - update to 5.10.0-328.0.0.229
bpftool-debuginfo - update to 5.10.0-328.0.0.229
kernel - update to 5.10.0-328.0.0.229
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/296c6a42b1174395935ca4cfe8f393e37b698d54
• https://git.kernel.org/stable/c/336340a0f8a141df8a4eb21a5a86f8ffb87769f6
• https://git.kernel.org/stable/c/4cd57ebee395041099fcdfcabb00749ce38d8b27
• https://git.kernel.org/stable/c/8f9903b0cdbb3155a8899410330b4b4d583a7a5c
• https://git.kernel.org/stable/c/99c21e7263248c3f084756bfae08163cc5d6c62f
• https://git.kernel.org/stable/c/9bd541e09dffff27e5bec0f9f45b0228173a5375
• https://git.kernel.org/stable/c/c5a125eadba05ba421c4b55e68da22b4a40d32b4
• https://git.kernel.org/stable/c/d2cd59fa848f9f13796ef214d3b1b5ca9a3fe21e

• Out-of-bounds read in Linux kernel ocfs2
• 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