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Fencer Vulns
critical 9.8

CVE-2026-52986 in the critical feed json

netfilter: nf_conntrack_sip: don't use simple_strtoul

published 2026-06-24 4 mo ago modified 2026-10-19 20 d ago also EUVD-2026-38854

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

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

netfilter: nf_conntrack_sip: don't use simple_strtoul

Replace unsafe port parsing in epaddr_len(), ct_sip_parse_header_uri(), and ct_sip_parse_request() with a new sip_parse_port() helper that validates each digit against the buffer limit, eliminating the use of simple_strtoul() which assumes NUL-terminated strings.

The previous code dereferenced pointers without bounds checks after sip_parse_addr() and relied on simple_strtoul() on non-NUL-terminated skb data. A port that reaches the buffer limit without a trailing character is also rejected as malformed.

Also get rid of all simple_strtoul() usage in conntrack, prefer a stricter version instead. There are intentional changes:

- Bail out if number is > UINT_MAX and indicate a failure, same for too long sequences. While we do accept 05535 as port 5535, we will not accept e.g. 'sip:10.0.0.1:005060'. While its syntactically valid under RFC 3261, we should restrict this to not waste cycles when presented with malformed packets with 64k '0' characters.

- Force base 10 in ct_sip_parse_numerical_param(). This is used to fetch 'expire=' and 'rports='; both are expected to use base-10.

- In nf_nat_sip.c, only accept the parsed value if its within the 1k-64k range.

- epaddr_len now returns 0 if the port is invalid, as it already does for invalid ip addresses. This is intentional. nf_conntrack_sip performs lots of guesswork to find the right parts of the message to parse. Being stricter could break existing setups. Connection tracking helpers are designed to allow traffic to pass, not to block it.

Based on an earlier patch from Jenny Guanni Qu <qguanni@gmail.com>.

Patch / fix

  • Linux Linux 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33, 7.0.10, 7.1
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.10-1

debian advisories DEBIAN-CVE-2026-52986

  • linux Ubuntu 22.04 LTS 5.15.0-186.196
  • linux Ubuntu 24.04 LTS 6.8.0-136.136
  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1112.119
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1061.64
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1112.122
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1064.72

ubuntu advisories UBUNTU-CVE-2026-52986

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-2026:76739RHSA-2026:66325RHSA-2026:66324

  • kernel-default SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Live Patching 15 SP6 +1 more 6.4.0-150600.23.130.1
  • kernel-64kb SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS, SLE High Performance Computing 15 SP5-ESPOS 5.14.21-150500.55.182.1
  • kernel-syms SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 5.14.21-150500.55.182.1
  • kernel-source SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 5.14.21-150500.55.182.1
  • kernel-default SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +3 more 5.14.21-150500.55.182.1
  • kernel-obs-build SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE High Performance Computing 15 SP5-LTSS +1 more 5.14.21-150500.55.182.1
  • kernel-default-base SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +2 more 5.14.21-150500.55.182.1.150500.6.85.2
  • kernel-rt Real Time Module 15 SP7 6.4.0-150700.7.72.1

suse advisories SUSE-SU-2026:3602-1SUSE-SU-2026:3595-1SUSE-SU-2026:3810-1SUSE-SU-2026:3809-1SUSE-SU-2026:3790-1SUSE-SU-2026:23244-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.37.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.37.1

opensuse advisories openSUSE-SU-2026:21555-1

  • kernel-rt AlmaLinux 8 4.18.0-553.162.1.rt7.503.el8_10
  • kernel-rt-core AlmaLinux 8 4.18.0-553.162.1.rt7.503.el8_10
  • kernel-rt-modules AlmaLinux 8 4.18.0-553.162.1.rt7.503.el8_10
  • kernel-rt-debug-core AlmaLinux 8 4.18.0-553.162.1.rt7.503.el8_10
  • kernel-rt-debug-modules AlmaLinux 8 4.18.0-553.162.1.rt7.503.el8_10
  • kernel-rt-modules-extra AlmaLinux 8 4.18.0-553.162.1.rt7.503.el8_10
  • kernel-rt-debug-modules-extra AlmaLinux 8 4.18.0-553.162.1.rt7.503.el8_10
  • kernel AlmaLinux 8 4.18.0-553.162.1.el8_10

almalinux advisories ALSA-2026:66324ALSA-2026:66325

  • kernel-rt Rocky Linux 8 4.18.0-553.162.1.rt7.503.el8_10
  • kernel Rocky Linux 8 4.18.0-553.162.1.el8_10

rocky linux advisories RLSA-2026:66324RLSA-2026:66325

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-2026-52986 updated cvss 7.0

kernel: netfilter: nf_conntrack_sip: don't use simple_strtoul

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more 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 5.14.0-687.55.1.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 BaseOS (v. 8) perf 4.18.0-553.162.1.el8_10, kernel 4.18.0-553.162.1.el8_10, bpftool 4.18.0-553.162.1.el8_10, kernel-core 4.18.0-553.162.1.el8_10, kernel-tools 4.18.0-553.162.1.el8_10, python3-perf 4.18.0-553.162.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:66325
  • 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 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 CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.162.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.162.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.162.1.el8_10
    fixed: vendor fix RHSA-2026:66325
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-kvm 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-core 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-modules 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-debug-kvm 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-debug-core 4.18.0-553.162.1.rt7.503.el8_10, +4 more
    fixed: vendor fix RHSA-2026:66324
  • 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 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
show 1 more
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-core 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-modules 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-debug-core 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-debug-modules 4.18.0-553.162.1.rt7.503.el8_10, kernel-rt-modules-extra 4.18.0-553.162.1.rt7.503.el8_10, +2 more
    fixed: vendor fix RHSA-2026:66324

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 ICSA-26-295-11 updated cvss 9.8

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.7 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.7
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
24 d ago

Exploit prediction

0.63% chance of exploitation in the next 30 days, higher than 50% 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
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

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.