Use-after-free in Linux kernel - CVE-2026-63994

Vulnerability identifier: #VU138658

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-2026-63994

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 a use-after-free in iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() when processing tunnel PMTU ICMP and ICMPv6 packet generation. A local user can trigger skb_cow() reallocation while stale network header pointers are still used to cause a denial of service.

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 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
python3-perf-debuginfo - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
python3-perf - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
perf-debuginfo - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
perf - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
kernel-tools-devel - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
kernel-tools-debuginfo - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
kernel-tools - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
kernel-source - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
kernel-headers - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
kernel-devel - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
kernel-debuginfo - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
bpftool-debuginfo - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
bpftool - addressed in versions 5.10.0-329.0.0.230, 6.6.0-145.3.29.160
kernel - addressed in versions 5.10.0-329.0.0.230, 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/50750d86a2e5266aba0c295483b3397843198b11
• https://git.kernel.org/stable/c/6dff77899b9e9fe5d854abda3a98ad04e7229ef7
• https://git.kernel.org/stable/c/7254aef4d1a7e18e887af9010e2f2dc34806789b
• https://git.kernel.org/stable/c/76cd9398a0470257ab765bdf5f358a2af2e17934
• https://git.kernel.org/stable/c/95b6d772bfe788331d9742d73eaa12e113b2adc4
• https://git.kernel.org/stable/c/b4bc94353050b1fa7b702bd4c6600710dd926cff
• https://git.kernel.org/stable/c/bf8b3f34c37c162357138e7c0942723b8b94fed1
• https://git.kernel.org/stable/c/f3f204541f280a6ecb04503a0d6794d93990ca43

• Use-after-free in Linux kernel ipv4
• 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