Out-of-bounds write in Linux kernel - CVE-2026-63923

Vulnerability identifier: #VU138728

CSH Severity: Low

CVSS v4: 6.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63923

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 or overwrite out-of-bounds memory.

The vulnerability exists due to an out-of-bounds write in rvu_mbox_handler_rep_event_notify and the representor event handling path when processing a crafted REP_EVENT_NOTIFY mailbox request with a sender-controlled body pcifunc value. A local user can send a specially crafted mailbox request to cause a denial of service or overwrite out-of-bounds memory.

Exploitation requires a VF attached to a PF that has been put into switchdev representor mode. For RVU_EVENT_MAC_ADDR_CHANGE, the invalid body pcifunc is used as a six-byte ether_addr_copy() target in the queued worker.

Linux kernel
SUSE Linux Enterprise High Availability Extension 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Workstation Extension 15
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
Development Tools Module
SUSE Linux Enterprise Live Patching
SUSE Real Time Module
Public Cloud Module
Legacy Module
Basesystem Module
Ubuntu
kernel-livepatch-SLE15-SP7-RT_Update_20-debugsource
kernel-livepatch-6_4_0-150700_7_75-rt
kernel-livepatch-6_4_0-150700_7_75-rt-debuginfo
kernel-livepatch-6_4_0-150700_53_81-default
kernel-livepatch-6_4_0-150700_53_81-default-debuginfo
kernel-livepatch-SLE15-SP7_Update_21-debugsource
kernel (Red Hat package)
gfs2-kmp-rt-debuginfo
ocfs2-kmp-rt
dlm-kmp-rt
kernel-rt-devel
kernel-rt-debugsource
kernel-rt-devel-debuginfo
kernel-rt
kernel-devel-rt
kernel-source-rt
cluster-md-kmp-rt-debuginfo
dlm-kmp-rt-debuginfo
gfs2-kmp-rt
kernel-rt-debuginfo
ocfs2-kmp-rt-debuginfo
kernel-syms-rt
cluster-md-kmp-rt
kernel-64kb
reiserfs-kmp-default-debuginfo
kernel-zfcpdump-debuginfo
kernel-zfcpdump-debugsource
kernel-zfcpdump
kernel-devel
kernel-macros
kernel-default-devel
kernel-default-devel-debuginfo
kernel-default
kernel-default-debugsource
cluster-md-kmp-default-debuginfo
dlm-kmp-default
gfs2-kmp-default-debuginfo
ocfs2-kmp-default
dlm-kmp-default-debuginfo
ocfs2-kmp-default-debuginfo
kernel-default-debuginfo
cluster-md-kmp-default
gfs2-kmp-default
kernel-64kb-devel
kernel-default-extra
kernel-default-extra-debuginfo
kernel-azure-devel-debuginfo
kernel-azure-debuginfo
kernel-azure-debugsource
kernel-azure-devel
kernel-azure
kernel-default-livepatch-devel
kernel-default-livepatch
reiserfs-kmp-default
kernel-source
kernel-obs-build-debugsource
kernel-obs-build
kernel-syms
kernel-docs
kernel-64kb-debugsource
kernel-64kb-devel-debuginfo
kernel-64kb-debuginfo
kernel-default-base
rv (Red Hat package)
libperf (Red Hat package)
kernel-tools-libs-devel (Red Hat package)
kernel-cross-headers (Red Hat package)
kernel-modules-extra (Red Hat package)
kernel-tools (Red Hat package)
kernel-rt-modules-extra (Red Hat package)
kernel-rt-modules-core (Red Hat package)
kernel-rt-modules (Red Hat package)
kernel-rt-devel (Red Hat package)
kernel-rt-debug-modules-extra (Red Hat package)
kernel-rt-debug-modules-core (Red Hat package)
kernel-rt-debug-modules (Red Hat package)
kernel-rt-debug-devel (Red Hat package)
kernel-rt-debug-core (Red Hat package)
kernel-rt-debug (Red Hat package)
kernel-rt-core (Red Hat package)
kernel-rt (Red Hat package)
kernel-modules-extra-matched (Red Hat package)
kernel-tools-libs (Red Hat package)
kernel-modules-core (Red Hat package)
kernel-modules (Red Hat package)
kernel-headers (Red Hat package)
kernel-debug (Red Hat package)
kernel-debug-core (Red Hat package)
kernel-devel-matched (Red Hat package)
kernel-devel (Red Hat package)
kernel-debug-uki-virt (Red Hat package)
kernel-debug-modules-extra (Red Hat package)
kernel-debug-modules-core (Red Hat package)
kernel-debug-modules (Red Hat package)
kernel-debug-devel-matched (Red Hat package)
kernel-debug-devel (Red Hat package)
kernel-64k-debug-devel-matched (Red Hat package)
kernel-rt-64k-modules-extra (Red Hat package)
kernel-rt-64k-modules-core (Red Hat package)
kernel-rt-64k-modules (Red Hat package)
kernel-rt-64k-devel (Red Hat package)
kernel-rt-64k-debug-modules-extra (Red Hat package)
kernel-rt-64k-debug-modules-core (Red Hat package)
kernel-rt-64k-debug-modules (Red Hat package)
kernel-rt-64k-debug-devel (Red Hat package)
kernel-rt-64k-debug-core (Red Hat package)
kernel-rt-64k-debug (Red Hat package)
kernel-rt-64k-core (Red Hat package)
kernel-rt-64k (Red Hat package)
kernel-64k-devel-matched (Red Hat package)
kernel-64k-devel (Red Hat package)
kernel-64k-debug-devel (Red Hat package)
rtla (Red Hat package)
kernel-zfcpdump-modules-extra (Red Hat package)
kernel-zfcpdump-modules-core (Red Hat package)
kernel-zfcpdump-modules (Red Hat package)
kernel-zfcpdump-devel-matched (Red Hat package)
kernel-zfcpdump-devel (Red Hat package)
kernel-zfcpdump-core (Red Hat package)
kernel-zfcpdump (Red Hat package)
python3-perf (Red Hat package)
perf (Red Hat package)
kernel-uki-virt-addons (Red Hat package)
kernel-uki-virt (Red Hat package)
linux-ibm (Ubuntu package)
linux-aws (Ubuntu package)
linux-azure (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-azure-7.0 (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-livepatch-SLE15-SP7-RT_Update_20-debugsource - update to 1-150700.1.3.1
kernel-livepatch-6_4_0-150700_7_75-rt - update to 1-150700.1.3.1
kernel-livepatch-6_4_0-150700_7_75-rt-debuginfo - update to 1-150700.1.3.1
kernel-livepatch-6_4_0-150700_53_81-default - update to 1-150700.15.3.1
kernel-livepatch-6_4_0-150700_53_81-default-debuginfo - update to 1-150700.15.3.1
kernel-livepatch-SLE15-SP7_Update_21-debugsource - update to 1-150700.15.3.1
kernel (Red Hat package) - update to 5.14.0-687.48.1.el9_8
gfs2-kmp-rt-debuginfo - update to 6.4.0-150700.7.75.1
ocfs2-kmp-rt - update to 6.4.0-150700.7.75.1
dlm-kmp-rt - update to 6.4.0-150700.7.75.1
kernel-rt-devel - update to 6.4.0-150700.7.75.1
kernel-rt-debugsource - update to 6.4.0-150700.7.75.1
kernel-rt-devel-debuginfo - update to 6.4.0-150700.7.75.1
kernel-rt - update to 6.4.0-150700.7.75.1
kernel-devel-rt - update to 6.4.0-150700.7.75.1
kernel-source-rt - update to 6.4.0-150700.7.75.1
cluster-md-kmp-rt-debuginfo - update to 6.4.0-150700.7.75.1
dlm-kmp-rt-debuginfo - update to 6.4.0-150700.7.75.1
gfs2-kmp-rt - update to 6.4.0-150700.7.75.1
kernel-rt-debuginfo - update to 6.4.0-150700.7.75.1
ocfs2-kmp-rt-debuginfo - update to 6.4.0-150700.7.75.1
kernel-syms-rt - update to 6.4.0-150700.7.75.1
cluster-md-kmp-rt - update to 6.4.0-150700.7.75.1
kernel-64kb - update to 6.4.0-150700.53.81.1
reiserfs-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
kernel-zfcpdump-debuginfo - update to 6.4.0-150700.53.81.1
kernel-zfcpdump-debugsource - update to 6.4.0-150700.53.81.1
kernel-zfcpdump - update to 6.4.0-150700.53.81.1
kernel-devel - update to 6.4.0-150700.53.81.1
kernel-macros - update to 6.4.0-150700.53.81.1
kernel-default-devel - update to 6.4.0-150700.53.81.1
kernel-default-devel-debuginfo - update to 6.4.0-150700.53.81.1
kernel-default - update to 6.4.0-150700.53.81.1
kernel-default-debugsource - update to 6.4.0-150700.53.81.1
cluster-md-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
dlm-kmp-default - update to 6.4.0-150700.53.81.1
gfs2-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
ocfs2-kmp-default - update to 6.4.0-150700.53.81.1
dlm-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
ocfs2-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
kernel-default-debuginfo - update to 6.4.0-150700.53.81.1
cluster-md-kmp-default - update to 6.4.0-150700.53.81.1
gfs2-kmp-default - update to 6.4.0-150700.53.81.1
kernel-64kb-devel - update to 6.4.0-150700.53.81.1
kernel-default-extra - update to 6.4.0-150700.53.81.1
kernel-default-extra-debuginfo - update to 6.4.0-150700.53.81.1
kernel-azure-devel-debuginfo - update to 6.4.0-150700.53.81.1
kernel-azure-debuginfo - update to 6.4.0-150700.53.81.1
kernel-azure-debugsource - update to 6.4.0-150700.53.81.1
kernel-azure-devel - update to 6.4.0-150700.53.81.1
kernel-azure - update to 6.4.0-150700.53.81.1
kernel-default-livepatch-devel - update to 6.4.0-150700.53.81.1
kernel-default-livepatch - update to 6.4.0-150700.53.81.1
reiserfs-kmp-default - update to 6.4.0-150700.53.81.1
kernel-source - update to 6.4.0-150700.53.81.1
kernel-obs-build-debugsource - update to 6.4.0-150700.53.81.1
kernel-obs-build - update to 6.4.0-150700.53.81.1
kernel-syms - update to 6.4.0-150700.53.81.1
kernel-docs - update to 6.4.0-150700.53.81.1
kernel-64kb-debugsource - update to 6.4.0-150700.53.81.1
kernel-64kb-devel-debuginfo - update to 6.4.0-150700.53.81.1
kernel-64kb-debuginfo - update to 6.4.0-150700.53.81.1
kernel-default-base - update to 6.4.0-150700.53.81.1.150700.17.45.1
rv (Red Hat package) - update to 6.12.0-211.56.1.el10_2
libperf (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-tools-libs-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-cross-headers (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-modules-extra (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-tools (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-modules-extra (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-modules-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-modules (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-debug-modules-extra (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-debug-modules-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-debug-modules (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-debug-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-debug-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-debug (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-modules-extra-matched (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-tools-libs (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-modules-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-modules (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-headers (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-debug (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-debug-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-devel-matched (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-debug-uki-virt (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-debug-modules-extra (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-debug-modules-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-debug-modules (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-debug-devel-matched (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-debug-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-64k-debug-devel-matched (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-modules-extra (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-modules-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-modules (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-debug-modules-extra (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-debug-modules-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-debug-modules (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-debug-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-debug-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-debug (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-rt-64k (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-64k-devel-matched (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-64k-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-64k-debug-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
rtla (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-zfcpdump-modules-extra (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-zfcpdump-modules-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-zfcpdump-modules (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-zfcpdump-devel-matched (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-zfcpdump-devel (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-zfcpdump-core (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-zfcpdump (Red Hat package) - update to 6.12.0-211.56.1.el10_2
python3-perf (Red Hat package) - update to 6.12.0-211.56.1.el10_2
perf (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-uki-virt-addons (Red Hat package) - update to 6.12.0-211.56.1.el10_2
kernel-uki-virt (Red Hat package) - update to 6.12.0-211.56.1.el10_2
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-oracle-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-azure-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1
linux-nvidia (Ubuntu package) - addressed in versions 7.0.0-1016.16~24.04.1, 7.0.0-1016.16
linux-nvidia-bos (Ubuntu package) - update to 7.0.0-2016.16

• https://git.kernel.org/stable/c/2156a29aecfffa2eb7c558255690084efbe9f3b0
• https://git.kernel.org/stable/c/68be0260e2a02ff9b18a8678d5f8d1715fa20138

• Out-of-bounds write in Linux kernel octeontx2 af driver
• Ubuntu update for linux-ibm
• Ubuntu update for linux-azure
• Ubuntu update for linux-aws
• Ubuntu update for linux-nvidia-bos
• Ubuntu update for linux-nvidia
• Ubuntu update for linux-gcp-7.0
• Red Hat Enterprise Linux 9 update for kernel
• Red Hat Enterprise Linux 10 update for kernel
• SUSE update for the Linux Kernel
• Ubuntu update for linux-oracle-7.0
• Ubuntu update for linux-azure-7.0
• SUSE update for the Linux Kernel