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Fencer Vulns
critical 9.8

CVE-2026-63993 in the critical feed json

vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()

published 2026-07-19 3 mo ago modified 2026-10-19 20 d ago also EUVD-2026-45566

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()

skb_tunnel_check_pmtu() can change skb->head.

Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.

Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c.

Found by Sashiko.

Patch / fix

  • Linux Linux 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35, 7.0.12, 7.1
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-63993

  • linux Ubuntu 22.04 LTS 5.15.0-194.204
  • linux Ubuntu 24.04 LTS 6.8.0-142.142
  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1116.123
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1065.68
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1117.127
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1069.77

ubuntu advisories UBUNTU-CVE-2026-63993

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-687.55.1.el9_8
  • rv RHEL 9 5.14.0-687.55.1.el9_8
  • perf RHEL 9 5.14.0-687.55.1.el9_8
  • rtla RHEL 9 5.14.0-687.55.1.el9_8
  • libperf RHEL 9 5.14.0-687.55.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.55.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.55.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.55.1.el9_8

red hat advisories RHSA-2026:83707RHSA-2026:76739RHSA-2026:64775

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.84.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.84.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.84.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.84.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1.150700.17.47.1

suse advisories SUSE-SU-2026:4706-1SUSE-SU-2026:4640-1SUSE-SU-2026:24316-1SUSE-SU-2026:24315-1SUSE-SU-2026:24181-1SUSE-SU-2026:24182-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1

  • kernel Rocky Linux 10 6.12.0-211.52.1.el10_2

rocky linux advisories RLSA-2026:64775

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-63993 updated cvss 7.0

kernel: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()

  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available
  • Red Hat CodeReady Linux Builder EUS (v.9.6) libperf 5.14.0-570.152.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.152.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.152.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.152.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.152.1.el9_6
    fixed: vendor fix RHSA-2026:91492
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.55.1.el9_8, perf 5.14.0-687.55.1.el9_8, rtla 5.14.0-687.55.1.el9_8, python3-perf 5.14.0-687.55.1.el9_8, kernel-devel-matched 5.14.0-687.55.1.el9_8, kernel-64k-devel-matched 5.14.0-687.55.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.52.1.el10_2, perf 6.12.0-211.52.1.el10_2, rtla 6.12.0-211.52.1.el10_2, python3-perf 6.12.0-211.52.1.el10_2, kernel-devel-matched 6.12.0-211.52.1.el10_2, kernel-64k-devel-matched 6.12.0-211.52.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:64775
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) perf 5.14.0-284.200.1.el9_2, rtla 5.14.0-284.200.1.el9_2, kernel-devel-matched 5.14.0-284.200.1.el9_2, kernel-64k-devel-matched 5.14.0-284.200.1.el9_2, kernel-debug-devel-matched 5.14.0-284.200.1.el9_2, kernel-debuginfo-common-s390x 5.14.0-284.200.1.el9_2, +5 more
    fixed: vendor fix RHSA-2026:92993
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) rv 5.14.0-427.158.1.el9_4, perf 5.14.0-427.158.1.el9_4, rtla 5.14.0-427.158.1.el9_4, kernel-devel-matched 5.14.0-427.158.1.el9_4, kernel-64k-devel-matched 5.14.0-427.158.1.el9_4, kernel-debug-devel-matched 5.14.0-427.158.1.el9_4, +6 more
    fixed: vendor fix RHSA-2026:91489
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) rv 6.12.0-55.111.1.el10_0, perf 6.12.0-55.111.1.el10_0, rtla 6.12.0-55.111.1.el10_0, python3-perf 6.12.0-55.111.1.el10_0, kernel-devel-matched 6.12.0-55.111.1.el10_0, kernel-64k-devel-matched 6.12.0-55.111.1.el10_0, +7 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) rv 5.14.0-570.152.1.el9_6, perf 5.14.0-570.152.1.el9_6, rtla 5.14.0-570.152.1.el9_6, python3-perf 5.14.0-570.152.1.el9_6, kernel-devel-matched 5.14.0-570.152.1.el9_6, kernel-64k-devel-matched 5.14.0-570.152.1.el9_6, +7 more
    fixed: vendor fix RHSA-2026:91492
show 22 more
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.55.1.el9_8, kernel-64k 5.14.0-687.55.1.el9_8, kernel-core 5.14.0-687.55.1.el9_8, kernel-tools 5.14.0-687.55.1.el9_8, kernel-modules 5.14.0-687.55.1.el9_8, kernel-64k-core 5.14.0-687.55.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.52.1.el10_2, kernel-64k 6.12.0-211.52.1.el10_2, kernel-core 6.12.0-211.52.1.el10_2, kernel-tools 6.12.0-211.52.1.el10_2, kernel-modules 6.12.0-211.52.1.el10_2, kernel-64k-core 6.12.0-211.52.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:64775
  • Red Hat Enterprise Linux BaseOS E4S (v.9.2) bpftool 7.0.0-284.200.1.el9_2, kernel 5.14.0-284.200.1.el9_2, kernel-64k 5.14.0-284.200.1.el9_2, kernel-core 5.14.0-284.200.1.el9_2, kernel-tools 5.14.0-284.200.1.el9_2, python3-perf 5.14.0-284.200.1.el9_2, +28 more
    fixed: vendor fix RHSA-2026:92993
  • Red Hat Enterprise Linux BaseOS E4S (v.9.4) bpftool 7.3.0-427.158.1.el9_4, kernel 5.14.0-427.158.1.el9_4, kernel-64k 5.14.0-427.158.1.el9_4, kernel-core 5.14.0-427.158.1.el9_4, kernel-tools 5.14.0-427.158.1.el9_4, python3-perf 5.14.0-427.158.1.el9_4, +28 more
    fixed: vendor fix RHSA-2026:91489
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel 6.12.0-55.111.1.el10_0, kernel-64k 6.12.0-55.111.1.el10_0, kernel-core 6.12.0-55.111.1.el10_0, kernel-tools 6.12.0-55.111.1.el10_0, kernel-modules 6.12.0-55.111.1.el10_0, kernel-64k-core 6.12.0-55.111.1.el10_0, +27 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) kernel 5.14.0-570.152.1.el9_6, kernel-64k 5.14.0-570.152.1.el9_6, kernel-core 5.14.0-570.152.1.el9_6, kernel-tools 5.14.0-570.152.1.el9_6, kernel-modules 5.14.0-570.152.1.el9_6, kernel-64k-core 5.14.0-570.152.1.el9_6, +27 more
    fixed: vendor fix RHSA-2026:91492
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.55.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.55.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.55.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.55.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.55.1.el9_8
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.52.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.52.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.52.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.52.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.52.1.el10_2
    fixed: vendor fix RHSA-2026:64775
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libperf 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.111.1.el10_0
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.55.1.el9_8, kernel-rt-64k 5.14.0-687.55.1.el9_8, kernel-rt-core 5.14.0-687.55.1.el9_8, kernel-rt-modules 5.14.0-687.55.1.el9_8, kernel-rt-64k-core 5.14.0-687.55.1.el9_8, kernel-rt-debug-core 5.14.0-687.55.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.52.1.el10_2, kernel-rt-64k 6.12.0-211.52.1.el10_2, kernel-rt-core 6.12.0-211.52.1.el10_2, kernel-rt-modules 6.12.0-211.52.1.el10_2, kernel-rt-64k-core 6.12.0-211.52.1.el10_2, kernel-rt-debug-core 6.12.0-211.52.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:64775
  • Red Hat Enterprise Linux Real Time E4S (v.9.2) kernel-rt 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-core 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-modules 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-debug-core 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-modules-core 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-debug-modules 5.14.0-284.200.1.rt14.485.el9_2, +4 more
    fixed: vendor fix RHSA-2026:93047
  • Red Hat Enterprise Linux Real Time E4S (v.9.4) kernel-rt 5.14.0-427.158.1.el9_4, kernel-rt-core 5.14.0-427.158.1.el9_4, kernel-rt-modules 5.14.0-427.158.1.el9_4, kernel-rt-debug-core 5.14.0-427.158.1.el9_4, kernel-rt-modules-core 5.14.0-427.158.1.el9_4, kernel-rt-debug-modules 5.14.0-427.158.1.el9_4, +4 more
    fixed: vendor fix RHSA-2026:91489
  • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt 6.12.0-55.111.1.el10_0, kernel-rt-64k 6.12.0-55.111.1.el10_0, kernel-rt-core 6.12.0-55.111.1.el10_0, kernel-rt-modules 6.12.0-55.111.1.el10_0, kernel-rt-64k-core 6.12.0-55.111.1.el10_0, kernel-rt-debug-core 6.12.0-55.111.1.el10_0, +14 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Real Time EUS (v.9.6) kernel-rt 5.14.0-570.152.1.el9_6, kernel-rt-64k 5.14.0-570.152.1.el9_6, kernel-rt-core 5.14.0-570.152.1.el9_6, kernel-rt-modules 5.14.0-570.152.1.el9_6, kernel-rt-64k-core 5.14.0-570.152.1.el9_6, kernel-rt-debug-core 5.14.0-570.152.1.el9_6, +14 more
    fixed: vendor fix RHSA-2026:91492
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.55.1.el9_8, kernel-rt-core 5.14.0-687.55.1.el9_8, kernel-rt-modules 5.14.0-687.55.1.el9_8, kernel-rt-debug-core 5.14.0-687.55.1.el9_8, kernel-rt-modules-core 5.14.0-687.55.1.el9_8, kernel-rt-debug-modules 5.14.0-687.55.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.52.1.el10_2, kernel-rt-core 6.12.0-211.52.1.el10_2, kernel-rt-modules 6.12.0-211.52.1.el10_2, kernel-rt-debug-core 6.12.0-211.52.1.el10_2, kernel-rt-modules-core 6.12.0-211.52.1.el10_2, kernel-rt-debug-modules 6.12.0-211.52.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:64775
  • Red Hat Enterprise Linux Real Time for NFV E4S (v.9.2) kernel-rt 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-kvm 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-core 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-modules 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-debug-kvm 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-debug-core 5.14.0-284.200.1.rt14.485.el9_2, +6 more
    fixed: vendor fix RHSA-2026:93047
  • Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4) kernel-rt 5.14.0-427.158.1.el9_4, kernel-rt-kvm 5.14.0-427.158.1.el9_4, kernel-rt-core 5.14.0-427.158.1.el9_4, kernel-rt-modules 5.14.0-427.158.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.158.1.el9_4, kernel-rt-debug-core 5.14.0-427.158.1.el9_4, +6 more
    fixed: vendor fix RHSA-2026:91489
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt 6.12.0-55.111.1.el10_0, kernel-rt-kvm 6.12.0-55.111.1.el10_0, kernel-rt-core 6.12.0-55.111.1.el10_0, kernel-rt-modules 6.12.0-55.111.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.111.1.el10_0, kernel-rt-debug-core 6.12.0-55.111.1.el10_0, +6 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6) kernel-rt 5.14.0-570.152.1.el9_6, kernel-rt-kvm 5.14.0-570.152.1.el9_6, kernel-rt-core 5.14.0-570.152.1.el9_6, kernel-rt-modules 5.14.0-570.152.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.152.1.el9_6, kernel-rt-debug-core 5.14.0-570.152.1.el9_6, +6 more
    fixed: vendor fix RHSA-2026:91492
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.51% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.