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Fencer Vulns
critical 9.8

CVE-2025-38472 in the critical feed json

netfilter: nf_conntrack: fix crash due to removal of uninitialised entry

published 2025-07-28 15 mo ago modified 2026-10-15 24 d ago also EUVD-2025-22890

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 40%
public exploits
0
none known

Summary

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

netfilter: nf_conntrack: fix crash due to removal of uninitialised entry

A crash in conntrack was reported while trying to unlink the conntrack entry from the hash bucket list: [exception RIP: __nf_ct_delete_from_lists+172] [..] #7 [ff539b5a2b043aa0] nf_ct_delete at ffffffffc124d421 [nf_conntrack] #8 [ff539b5a2b043ad0] nf_ct_gc_expired at ffffffffc124d999 [nf_conntrack] #9 [ff539b5a2b043ae0] __nf_conntrack_find_get at ffffffffc124efbc [nf_conntrack] [..]

The nf_conn struct is marked as allocated from slab but appears to be in a partially initialised state:

ct hlist pointer is garbage; looks like the ct hash value (hence crash). ct->status is equal to IPS_CONFIRMED|IPS_DYING, which is expected ct->timeout is 30000 (=30s), which is unexpected.

Everything else looks like normal udp conntrack entry. If we ignore ct->status and pretend its 0, the entry matches those that are newly allocated but not yet inserted into the hash: - ct hlist pointers are overloaded and store/cache the raw tuple hash - ct->timeout matches the relative time expected for a new udp flow rather than the absolute 'jiffies' value.

If it were not for the presence of IPS_CONFIRMED, __nf_conntrack_find_get() would have skipped the entry.

Theory is that we did hit following race:

cpu x cpu y cpu z found entry E found entry E E is expired <preemption> nf_ct_delete() return E to rcu slab init_conntrack E is re-inited, ct->status set to 0 reply tuplehash hnnode.pprev stores hash value.

cpu y found E right before it was deleted on cpu x. E is now re-inited on cpu z. cpu y was preempted before checking for expiry and/or confirm bit.

->refcnt set to 1 E now owned by skb ->timeout set to 30000

If cpu y were to resume now, it would observe E as expired but would skip E due to missing CONFIRMED bit.

nf_conntrack_confirm gets called sets: ct->status |= CONFIRMED This is wrong: E is not yet added to hashtable.

cpu y resumes, it observes E as expired but CONFIRMED: <resumes> nf_ct_expired() -> yes (ct->timeout is 30s) confirmed bit set.

cpu y will try to delete E from the hashtable: nf_ct_delete() -> set DYING bit __nf_ct_delete_from_lists

Even this scenario doesn't guarantee a crash: cpu z still holds the table bucket lock(s) so y blocks:

wait for spinlock held by z

CONFIRMED is set but there is no guarantee ct will be added to hash: "chaintoolong" or "clash resolution" logic both skip the insert step. reply hnnode.pprev still stores the hash value.

unlocks spinlock return NF_DROP <unblocks, then crashes on hlist_nulls_del_rcu pprev>

In case CPU z does insert the entry into the hashtable, cpu y will unlink E again right away but no crash occurs.

Without 'cpu y' race, 'garbage' hlist is of no consequence: ct refcnt remains at 1, eventually skb will be free'd and E gets destroyed via: nf_conntrack_put -> nf_conntrack_destroy -> nf_ct_destroy.

To resolve this, move the IPS_CONFIRMED assignment after the table insertion but before the unlock.

Pablo points out that the confirm-bit-store could be reordered to happen before hlist add resp. the timeout fixup, so switch to set_bit and before_atomic memory barrier to prevent this.

It doesn't matter if other CPUs can observe a newly inserted entry right before the CONFIRMED bit was set:

Such event cannot be distinguished from above "E is the old incarnation" case: the entry will be skipped.

Also change nf_ct_should_gc() to first check the confirmed bit.

The gc sequence is: 1. Check if entry has expired, if not skip to next entry 2. Obtain a reference to the expired entry. 3. Call nf_ct_should_gc() to double-check step 1.

nf_ct_should_gc() is thus called only for entries that already failed an expiry check. After this patch, once the confirmed bit check pas ---truncated---

Patch / fix

  • Linux Linux 5.19, 6.1.147, 6.6.100, 6.12.40, 6.15.8, 6.16
  • linux Debian 12 6.1.147-1
  • linux Debian 13 6.12.41-1
  • linux Debian 14 6.16.3-1

debian advisories DEBIAN-CVE-2025-38472

  • linux Ubuntu 24.04 LTS 6.8.0-100.100
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1046.49
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1047.50
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1043.48
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1044.44
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1046.52
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1030.33
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1047.51

ubuntu advisories UBUNTU-CVE-2025-38472

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 5.14.0-570.49.1.el9_6
  • rv RHEL 9 5.14.0-570.49.1.el9_6
  • perf RHEL 9 5.14.0-570.49.1.el9_6
  • rtla RHEL 9 5.14.0-570.49.1.el9_6
  • libperf RHEL 9 5.14.0-570.49.1.el9_6
  • kernel-rt RHEL 9 5.14.0-570.49.1.el9_6
  • kernel-64k RHEL 9 5.14.0-570.49.1.el9_6
  • kernel-core RHEL 9 5.14.0-570.49.1.el9_6

red hat advisories RHSA-2025:17241RHSA-2025:17123RHSA-2025:17122RHSA-2025:16880RHSA-2025:15005

  • kernel-rt Linux Micro 6.2 6.12.0-160000.6.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.6.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.6.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.6.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.6.1.160000.2.4
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.6.1
  • kernel-obs-qa SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.6.1
  • kernel-kvmsmall SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.6.1

suse advisories SUSE-SU-2025:21074-1SUSE-SU-2025:21139-1SUSE-SU-2026:20560-1SUSE-SU-2025:21179-1SUSE-SU-2025:03634-1SUSE-SU-2025:03633-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.6.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.6.1
  • kernel-kvmsmall openSUSE Leap 16.0 6.12.0-160000.6.1

opensuse advisories openSUSE-SU-2025:20081-1

  • kernel AlmaLinux 9 5.14.0-570.49.1.el9_6
  • rv AlmaLinux 9 5.14.0-570.49.1.el9_6
  • perf AlmaLinux 9 5.14.0-570.49.1.el9_6
  • rtla AlmaLinux 9 5.14.0-570.49.1.el9_6
  • libperf AlmaLinux 9 5.14.0-570.49.1.el9_6
  • kernel-rt AlmaLinux 9 5.14.0-570.49.1.el9_6
  • kernel-64k AlmaLinux 9 5.14.0-570.49.1.el9_6
  • kernel-core AlmaLinux 9 5.14.0-570.49.1.el9_6

almalinux advisories ALSA-2025:16880ALSA-2025:15005

  • kernel Rocky Linux 9 5.14.0-570.49.1.el9_6
  • kernel Rocky Linux 10 6.12.0-55.30.1.el10_0

rocky linux advisories RLSA-2025:16880RLSA-2025:15005

  • kernel Azure Linux 3.0 6.6.104.2-1

azure linux advisories AZL-65892

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2025-38472 updated cvss 7.1

kernel: netfilter: nf_conntrack: fix crash due to removal of uninitialised entry

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • 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: workaround, no fix available
  • Red Hat CodeReady Linux Builder EUS (v.9.4) libperf 5.14.0-427.92.1.el9_4, kernel-debuginfo-common-s390x 5.14.0-427.92.1.el9_4, kernel-debuginfo-common-x86_64 5.14.0-427.92.1.el9_4, kernel-debuginfo-common-aarch64 5.14.0-427.92.1.el9_4, kernel-debuginfo-common-ppc64le 5.14.0-427.92.1.el9_4
    fixed: vendor fix RHSA-2025:17241
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-570.49.1.el9_6, perf 5.14.0-570.49.1.el9_6, rtla 5.14.0-570.49.1.el9_6, python3-perf 5.14.0-570.49.1.el9_6, kernel-devel-matched 5.14.0-570.49.1.el9_6, kernel-64k-devel-matched 5.14.0-570.49.1.el9_6, +7 more
    fixed: vendor fix RHSA-2025:16880
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-55.30.1.el10_0, perf 6.12.0-55.30.1.el10_0, rtla 6.12.0-55.30.1.el10_0, python3-perf 6.12.0-55.30.1.el10_0, kernel-devel-matched 6.12.0-55.30.1.el10_0, kernel-64k-devel-matched 6.12.0-55.30.1.el10_0, +7 more
    fixed: vendor fix RHSA-2025:15005
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) perf 5.14.0-284.140.1.el9_2, rtla 5.14.0-284.140.1.el9_2, kernel-devel-matched 5.14.0-284.140.1.el9_2, kernel-64k-devel-matched 5.14.0-284.140.1.el9_2, kernel-debug-devel-matched 5.14.0-284.140.1.el9_2, kernel-debuginfo-common-s390x 5.14.0-284.140.1.el9_2, +5 more
    fixed: vendor fix RHSA-2025:17122
  • Red Hat Enterprise Linux AppStream EUS (v.9.4) rv 5.14.0-427.92.1.el9_4, perf 5.14.0-427.92.1.el9_4, rtla 5.14.0-427.92.1.el9_4, kernel-devel-matched 5.14.0-427.92.1.el9_4, kernel-64k-devel-matched 5.14.0-427.92.1.el9_4, kernel-debug-devel-matched 5.14.0-427.92.1.el9_4, +6 more
    fixed: vendor fix RHSA-2025:17241
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-570.49.1.el9_6, kernel-64k 5.14.0-570.49.1.el9_6, kernel-core 5.14.0-570.49.1.el9_6, kernel-tools 5.14.0-570.49.1.el9_6, kernel-modules 5.14.0-570.49.1.el9_6, kernel-64k-core 5.14.0-570.49.1.el9_6, +27 more
    fixed: vendor fix RHSA-2025:16880
show 14 more
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-55.30.1.el10_0, kernel-64k 6.12.0-55.30.1.el10_0, kernel-core 6.12.0-55.30.1.el10_0, kernel-tools 6.12.0-55.30.1.el10_0, kernel-modules 6.12.0-55.30.1.el10_0, kernel-64k-core 6.12.0-55.30.1.el10_0, +27 more
    fixed: vendor fix RHSA-2025:15005
  • Red Hat Enterprise Linux BaseOS E4S (v.9.2) bpftool 7.0.0-284.140.1.el9_2, kernel 5.14.0-284.140.1.el9_2, kernel-64k 5.14.0-284.140.1.el9_2, kernel-core 5.14.0-284.140.1.el9_2, kernel-tools 5.14.0-284.140.1.el9_2, python3-perf 5.14.0-284.140.1.el9_2, +28 more
    fixed: vendor fix RHSA-2025:17122
  • Red Hat Enterprise Linux BaseOS EUS (v.9.4) bpftool 7.3.0-427.92.1.el9_4, kernel 5.14.0-427.92.1.el9_4, kernel-64k 5.14.0-427.92.1.el9_4, kernel-core 5.14.0-427.92.1.el9_4, kernel-tools 5.14.0-427.92.1.el9_4, python3-perf 5.14.0-427.92.1.el9_4, +28 more
    fixed: vendor fix RHSA-2025:17241
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-570.49.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.49.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.49.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.49.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.49.1.el9_6
    fixed: vendor fix RHSA-2025:16880
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-55.30.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.30.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.30.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.30.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.30.1.el10_0
    fixed: vendor fix RHSA-2025:15005
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-570.49.1.el9_6, kernel-rt-64k 5.14.0-570.49.1.el9_6, kernel-rt-core 5.14.0-570.49.1.el9_6, kernel-rt-modules 5.14.0-570.49.1.el9_6, kernel-rt-64k-core 5.14.0-570.49.1.el9_6, kernel-rt-debug-core 5.14.0-570.49.1.el9_6, +14 more
    fixed: vendor fix RHSA-2025:16880
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-55.30.1.el10_0, kernel-rt-64k 6.12.0-55.30.1.el10_0, kernel-rt-core 6.12.0-55.30.1.el10_0, kernel-rt-modules 6.12.0-55.30.1.el10_0, kernel-rt-64k-core 6.12.0-55.30.1.el10_0, kernel-rt-debug-core 6.12.0-55.30.1.el10_0, +14 more
    fixed: vendor fix RHSA-2025:15005
  • Red Hat Enterprise Linux Real Time E4S (v.9.2) kernel-rt 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-core 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-modules 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-debug-core 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-modules-core 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-debug-modules 5.14.0-284.140.1.rt14.425.el9_2, +4 more
    fixed: vendor fix RHSA-2025:17123
  • Red Hat Enterprise Linux Real Time EUS (v.9.4) kernel-rt 5.14.0-427.92.1.el9_4, kernel-rt-core 5.14.0-427.92.1.el9_4, kernel-rt-modules 5.14.0-427.92.1.el9_4, kernel-rt-debug-core 5.14.0-427.92.1.el9_4, kernel-rt-modules-core 5.14.0-427.92.1.el9_4, kernel-rt-debug-modules 5.14.0-427.92.1.el9_4, +4 more
    fixed: vendor fix RHSA-2025:17241
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-570.49.1.el9_6, kernel-rt-kvm 5.14.0-570.49.1.el9_6, kernel-rt-core 5.14.0-570.49.1.el9_6, kernel-rt-modules 5.14.0-570.49.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.49.1.el9_6, kernel-rt-debug-core 5.14.0-570.49.1.el9_6, +6 more
    fixed: vendor fix RHSA-2025:16880
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-55.30.1.el10_0, kernel-rt-kvm 6.12.0-55.30.1.el10_0, kernel-rt-core 6.12.0-55.30.1.el10_0, kernel-rt-modules 6.12.0-55.30.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.30.1.el10_0, kernel-rt-debug-core 6.12.0-55.30.1.el10_0, +6 more
    fixed: vendor fix RHSA-2025:15005
  • Red Hat Enterprise Linux Real Time for NFV E4S (v.9.2) kernel-rt 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-kvm 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-core 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-modules 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-debug-kvm 5.14.0-284.140.1.rt14.425.el9_2, kernel-rt-debug-core 5.14.0-284.140.1.rt14.425.el9_2, +6 more
    fixed: vendor fix RHSA-2025:17123
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.4) kernel-rt 5.14.0-427.92.1.el9_4, kernel-rt-kvm 5.14.0-427.92.1.el9_4, kernel-rt-core 5.14.0-427.92.1.el9_4, kernel-rt-modules 5.14.0-427.92.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.92.1.el9_4, kernel-rt-debug-core 5.14.0-427.92.1.el9_4, +6 more
    fixed: vendor fix RHSA-2025:17241
  • 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
24 d ago

Exploit prediction

0.46% chance of exploitation in the next 30 days, higher than 40% 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
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-908 Use of Uninitialized Resource
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.