Skip to content
Fencer Vulns
critical 9.8

CVE-2026-64007 in the critical feed json

netfilter: synproxy: refresh tcphdr after skb_ensure_writable

published 2026-07-19 3 mo ago modified 2026-10-19 20 d ago also EUVD-2026-45580

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:

netfilter: synproxy: refresh tcphdr after skb_ensure_writable

synproxy_tstamp_adjust() rewrites the TCP timestamp option in place and then patches the TCP checksum via inet_proto_csum_replace4() on the caller-supplied tcphdr pointer. Both ipv4_synproxy_hook() and ipv6_synproxy_hook() obtain that pointer with skb_header_pointer() before calling in, so it may either alias skb->head directly or point at the caller's on-stack _tcph buffer.

Between obtaining the pointer and using it, the function calls skb_ensure_writable(skb, optend), which on a cloned or non-linear skb invokes pskb_expand_head() and frees the old skb->head. After that point the cached th is stale:

caller (ipv[46]_synproxy_hook) th = skb_header_pointer(skb, ..., &_tcph) synproxy_tstamp_adjust(skb, protoff, th, ...) skb_ensure_writable(skb, optend) pskb_expand_head() /* kfree(old skb->head) */ ... inet_proto_csum_replace4(&th->check, ...) /* writes into freed head, or into the caller's stack copy leaving the on-wire checksum stale */

The option bytes are written through skb->data and are fine; only the checksum update goes through th and so lands in the wrong place. The result is either a write into freed slab memory or a packet leaving with a checksum that does not match its payload.

Fix by re-deriving th from skb->data + protoff immediately after skb_ensure_writable() succeeds, so the subsequent checksum update targets the linear, writable header.

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-2026-64007

  • 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-2026-64007

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 8 4.18.0-553.160.1.el8_10
  • perf RHEL 8 4.18.0-553.160.1.el8_10
  • bpftool RHEL 8 4.18.0-553.160.1.el8_10
  • kernel-core RHEL 8 4.18.0-553.160.1.el8_10
  • kernel-tools RHEL 8 4.18.0-553.160.1.el8_10
  • python3-perf RHEL 8 4.18.0-553.160.1.el8_10
  • kernel-modules RHEL 8 4.18.0-553.160.1.el8_10
  • kernel-zfcpdump RHEL 8 4.18.0-553.160.1.el8_10

red hat advisories RHSA-2026:81371RHSA-2026:81349RHSA-2026:77634RHSA-2026:77218RHSA-2026:77217RHSA-2026:77216

  • kernel-64kb SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS, SLE High Performance Computing 15 SP5-ESPOS 5.14.21-150500.55.189.1
  • kernel-syms SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 5.14.21-150500.55.189.1
  • kernel-source SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 5.14.21-150500.55.189.1
  • kernel-default SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +3 more 5.14.21-150500.55.189.1
  • kernel-obs-build SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 5.14.21-150500.55.189.1
  • kernel-default-base SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 5.14.21-150500.55.189.1.150500.6.87.4
  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1

suse advisories SUSE-SU-2026:4595-1SUSE-SU-2026:4254-1SUSE-SU-2026:4369-1SUSE-SU-2026:4347-1SUSE-SU-2026:4284-1SUSE-SU-2026:23887-1

  • 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 AlmaLinux 8 4.18.0-553.160.1.el8_10
  • perf AlmaLinux 8 4.18.0-553.160.1.el8_10
  • bpftool AlmaLinux 8 4.18.0-553.160.1.el8_10
  • kernel-core AlmaLinux 8 4.18.0-553.160.1.el8_10
  • kernel-tools AlmaLinux 8 4.18.0-553.160.1.el8_10
  • python3-perf AlmaLinux 8 4.18.0-553.160.1.el8_10
  • kernel-modules AlmaLinux 8 4.18.0-553.160.1.el8_10
  • kernel-zfcpdump AlmaLinux 8 4.18.0-553.160.1.el8_10

almalinux advisories ALSA-2026:66000ALSA-2026:64770ALSA-2026:57252

  • kernel-rt Rocky Linux 8 4.18.0-553.160.1.rt7.501.el8_10
  • kernel Rocky Linux 9 5.14.0-687.41.1.el9_8

rocky linux advisories RLSA-2026:64770RLSA-2026:57252

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-2026-64007 updated cvss 7.0

kernel: netfilter: synproxy: refresh tcphdr after skb_ensure_writable

  • 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 Red Hat Enterprise Linux 10 kernel
    affected: no fix available
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.41.1.el9_8, perf 5.14.0-687.41.1.el9_8, rtla 5.14.0-687.41.1.el9_8, python3-perf 5.14.0-687.41.1.el9_8, kernel-devel-matched 5.14.0-687.41.1.el9_8, kernel-64k-devel-matched 5.14.0-687.41.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) perf 5.14.0-284.202.1.el9_2, rtla 5.14.0-284.202.1.el9_2, kernel-devel-matched 5.14.0-284.202.1.el9_2, kernel-64k-devel-matched 5.14.0-284.202.1.el9_2, kernel-debug-devel-matched 5.14.0-284.202.1.el9_2, kernel-debuginfo-common-s390x 5.14.0-284.202.1.el9_2, +5 more
    fixed: vendor fix RHSA-2026:94477
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) rv 5.14.0-427.154.1.el9_4, perf 5.14.0-427.154.1.el9_4, rtla 5.14.0-427.154.1.el9_4, kernel-devel-matched 5.14.0-427.154.1.el9_4, kernel-64k-devel-matched 5.14.0-427.154.1.el9_4, kernel-debug-devel-matched 5.14.0-427.154.1.el9_4, +6 more
    fixed: vendor fix RHSA-2026:77218
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) rv 6.12.0-55.109.1.el10_0, perf 6.12.0-55.109.1.el10_0, rtla 6.12.0-55.109.1.el10_0, python3-perf 6.12.0-55.109.1.el10_0, kernel-devel-matched 6.12.0-55.109.1.el10_0, kernel-64k-devel-matched 6.12.0-55.109.1.el10_0, +7 more
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.160.1.el8_10, kernel 4.18.0-553.160.1.el8_10, bpftool 4.18.0-553.160.1.el8_10, kernel-core 4.18.0-553.160.1.el8_10, kernel-tools 4.18.0-553.160.1.el8_10, python3-perf 4.18.0-553.160.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:66000
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.41.1.el9_8, kernel-64k 5.14.0-687.41.1.el9_8, kernel-core 5.14.0-687.41.1.el9_8, kernel-tools 5.14.0-687.41.1.el9_8, kernel-modules 5.14.0-687.41.1.el9_8, kernel-64k-core 5.14.0-687.41.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) perf 4.18.0-305.211.1.el8_4, kernel 4.18.0-305.211.1.el8_4, bpftool 4.18.0-305.211.1.el8_4, kernel-core 4.18.0-305.211.1.el8_4, kernel-tools 4.18.0-305.211.1.el8_4, python3-perf 4.18.0-305.211.1.el8_4, +8 more
    fixed: vendor fix RHSA-2026:77217
show 22 more
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) perf 4.18.0-372.220.1.el8_6, kernel 4.18.0-372.220.1.el8_6, bpftool 4.18.0-372.220.1.el8_6, kernel-core 4.18.0-372.220.1.el8_6, kernel-tools 4.18.0-372.220.1.el8_6, python3-perf 4.18.0-372.220.1.el8_6, +8 more
    fixed: vendor fix RHSA-2026:77216
  • Red Hat Enterprise Linux BaseOS E4S (v.9.2) bpftool 7.0.0-284.202.1.el9_2, kernel 5.14.0-284.202.1.el9_2, kernel-64k 5.14.0-284.202.1.el9_2, kernel-core 5.14.0-284.202.1.el9_2, kernel-tools 5.14.0-284.202.1.el9_2, python3-perf 5.14.0-284.202.1.el9_2, +28 more
    fixed: vendor fix RHSA-2026:94477
  • Red Hat Enterprise Linux BaseOS E4S (v.9.4) bpftool 7.3.0-427.154.1.el9_4, kernel 5.14.0-427.154.1.el9_4, kernel-64k 5.14.0-427.154.1.el9_4, kernel-core 5.14.0-427.154.1.el9_4, kernel-tools 5.14.0-427.154.1.el9_4, python3-perf 5.14.0-427.154.1.el9_4, +28 more
    fixed: vendor fix RHSA-2026:77218
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel 6.12.0-55.109.1.el10_0, kernel-64k 6.12.0-55.109.1.el10_0, kernel-core 6.12.0-55.109.1.el10_0, kernel-tools 6.12.0-55.109.1.el10_0, kernel-modules 6.12.0-55.109.1.el10_0, kernel-64k-core 6.12.0-55.109.1.el10_0, +27 more
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) perf 4.18.0-305.211.1.el8_4, kernel 4.18.0-305.211.1.el8_4, bpftool 4.18.0-305.211.1.el8_4, kernel-core 4.18.0-305.211.1.el8_4, kernel-tools 4.18.0-305.211.1.el8_4, python3-perf 4.18.0-305.211.1.el8_4, +15 more
    fixed: vendor fix RHSA-2026:77217
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) perf 4.18.0-372.220.1.el8_6, kernel 4.18.0-372.220.1.el8_6, bpftool 4.18.0-372.220.1.el8_6, kernel-core 4.18.0-372.220.1.el8_6, kernel-tools 4.18.0-372.220.1.el8_6, python3-perf 4.18.0-372.220.1.el8_6, +15 more
    fixed: vendor fix RHSA-2026:77216
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.41.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.41.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.41.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.41.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.41.1.el9_8
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libperf 6.12.0-55.109.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.109.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.109.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.109.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.109.1.el10_0
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.160.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.160.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.160.1.el8_10
    fixed: vendor fix RHSA-2026:66000
  • Red Hat Enterprise Linux for Real Time (v. 7 ELS) kernel-rt 3.10.0-1160.167.1.rt56.1319.el7, kernel-rt-trace 3.10.0-1160.167.1.rt56.1319.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.167.1.rt56.1319.el7
    fixed: vendor fix RHSA-2026:81371
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-kvm 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-core 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-modules 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-debug-kvm 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-debug-core 4.18.0-553.160.1.rt7.501.el8_10, +4 more
    fixed: vendor fix RHSA-2026:64770
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.41.1.el9_8, kernel-rt-64k 5.14.0-687.41.1.el9_8, kernel-rt-core 5.14.0-687.41.1.el9_8, kernel-rt-modules 5.14.0-687.41.1.el9_8, kernel-rt-64k-core 5.14.0-687.41.1.el9_8, kernel-rt-debug-core 5.14.0-687.41.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux Real Time E4S (v.9.2) kernel-rt 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-core 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-modules 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-debug-core 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-modules-core 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-debug-modules 5.14.0-284.202.1.rt14.487.el9_2, +4 more
    fixed: vendor fix RHSA-2026:94558
  • Red Hat Enterprise Linux Real Time E4S (v.9.4) kernel-rt 5.14.0-427.154.1.el9_4, kernel-rt-core 5.14.0-427.154.1.el9_4, kernel-rt-modules 5.14.0-427.154.1.el9_4, kernel-rt-debug-core 5.14.0-427.154.1.el9_4, kernel-rt-modules-core 5.14.0-427.154.1.el9_4, kernel-rt-debug-modules 5.14.0-427.154.1.el9_4, +4 more
    fixed: vendor fix RHSA-2026:77218
  • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt 6.12.0-55.109.1.el10_0, kernel-rt-64k 6.12.0-55.109.1.el10_0, kernel-rt-core 6.12.0-55.109.1.el10_0, kernel-rt-modules 6.12.0-55.109.1.el10_0, kernel-rt-64k-core 6.12.0-55.109.1.el10_0, kernel-rt-debug-core 6.12.0-55.109.1.el10_0, +14 more
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.41.1.el9_8, kernel-rt-core 5.14.0-687.41.1.el9_8, kernel-rt-modules 5.14.0-687.41.1.el9_8, kernel-rt-debug-core 5.14.0-687.41.1.el9_8, kernel-rt-modules-core 5.14.0-687.41.1.el9_8, kernel-rt-debug-modules 5.14.0-687.41.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:57252
  • Red Hat Enterprise Linux Real Time for NFV E4S (v.9.2) kernel-rt 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-kvm 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-core 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-modules 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-debug-kvm 5.14.0-284.202.1.rt14.487.el9_2, kernel-rt-debug-core 5.14.0-284.202.1.rt14.487.el9_2, +6 more
    fixed: vendor fix RHSA-2026:94558
  • Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4) kernel-rt 5.14.0-427.154.1.el9_4, kernel-rt-kvm 5.14.0-427.154.1.el9_4, kernel-rt-core 5.14.0-427.154.1.el9_4, kernel-rt-modules 5.14.0-427.154.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.154.1.el9_4, kernel-rt-debug-core 5.14.0-427.154.1.el9_4, +6 more
    fixed: vendor fix RHSA-2026:77218
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt 6.12.0-55.109.1.el10_0, kernel-rt-kvm 6.12.0-55.109.1.el10_0, kernel-rt-core 6.12.0-55.109.1.el10_0, kernel-rt-modules 6.12.0-55.109.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.109.1.el10_0, kernel-rt-debug-core 6.12.0-55.109.1.el10_0, +6 more
    fixed: vendor fix RHSA-2026:77634
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-core 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-modules 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-debug-core 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-debug-modules 4.18.0-553.160.1.rt7.501.el8_10, kernel-rt-modules-extra 4.18.0-553.160.1.rt7.501.el8_10, +2 more
    fixed: vendor fix RHSA-2026:64770
  • Red Hat Enterprise Linux Server (v. 7 ELS) perf 3.10.0-1160.167.1.el7, kernel 3.10.0-1160.167.1.el7, bpftool 3.10.0-1160.167.1.el7, python-perf 3.10.0-1160.167.1.el7, kernel-kdump 3.10.0-1160.167.1.el7, kernel-tools 3.10.0-1160.167.1.el7, +7 more Red Hat Enterprise Linux Server Optional (v. 7 ELS) kernel-debuginfo-common-ppc64 3.10.0-1160.167.1.el7, kernel-debuginfo-common-x86_64 3.10.0-1160.167.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1160.167.1.el7
    fixed: vendor fix RHSA-2026:81349
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 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.