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Fencer Vulns
medium 5.5

CVE-2026-46086 json

net: bridge: use a stable FDB dst snapshot in RCU readers

published 2026-05-27 5 mo ago modified 2026-11-06 2 d ago also EUVD-2026-32469

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

Summary

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

net: bridge: use a stable FDB dst snapshot in RCU readers

Local FDB entries can be rewritten in place by `fdb_delete_local()`, which updates `f->dst` to another port or to `NULL` while keeping the entry alive. Several bridge RCU readers inspect `f->dst`, including `br_fdb_fillbuf()` through the `brforward_read()` sysfs path.

These readers currently load `f->dst` multiple times and can therefore observe inconsistent values across the check and later dereference. In `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change `f->dst` after the NULL check and before the `port_no` dereference, leading to a NULL-ptr-deref.

Fix this by taking a single `READ_ONCE()` snapshot of `f->dst` in each affected RCU reader and using that snapshot for the rest of the access sequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()` with `WRITE_ONCE()` so the readers and writer use matching access patterns.

Patch / fix

  • Linux Linux 5.10.259, 5.15.210, 6.1.176, 6.6.140, 6.12.86, 6.18.27, 7.0.4, 7.1
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.86-1
  • linux Debian 14 7.0.4-1

debian advisories DEBIAN-CVE-2026-46086

  • linux Ubuntu 22.04 LTS 5.15.0-198.208
  • linux Ubuntu 24.04 LTS 6.8.0-136.136
  • linux Ubuntu 26.04 LTS 7.0.0-27.27
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1117.124
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1061.64
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1008.8
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1118.128
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1064.72

ubuntu advisories UBUNTU-CVE-2026-46086

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 10.2 6.12.0-211.40.1.el10_2
  • rv RHEL 10.2 6.12.0-211.40.1.el10_2
  • perf RHEL 10.2 6.12.0-211.40.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.40.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.40.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.40.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.40.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.40.1.el10_2

red hat advisories RHSA-2026:47017RHSA-2026:39180RHSA-2026:39179RHSA-2026:38491

  • kernel-source Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-default Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-kvmsmall Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.37.1
  • kernel-rt Linux Micro 6.2 6.12.0-160000.37.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.37.1

suse advisories SUSE-SU-2026:23244-1SUSE-SU-2026:23241-1SUSE-SU-2026:23194-1SUSE-SU-2026:23193-1SUSE-SU-2026:3594-1SUSE-SU-2026:23237-1

  • 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-2026:21555-1openSUSE-SU-2026:10954-1

  • kernel AlmaLinux 10 6.12.0-211.40.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.40.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.40.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.40.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.40.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.40.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.40.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.40.1.el10_2

almalinux advisories ALSA-2026:47017ALSA-2026:39179ALSA-2026:39180ALSA-2026:38491

  • kernel Rocky Linux 10 6.12.0-211.40.1.el10_2
  • kernel-rt Rocky Linux 8 4.18.0-553.144.1.rt7.485.el8_10
  • kernel Rocky Linux 8 4.18.0-553.144.1.el8_10
  • kernel Rocky Linux 9 5.14.0-687.25.1.el9_8

rocky linux advisories RLSA-2026:47017RLSA-2026:39180RLSA-2026:39179RLSA-2026:38491

  • kernel Azure Linux 3.0 6.6.141.1-1

azure linux advisories AZL-88512

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-2026-46086 updated cvss 4.7

kernel: net: bridge: use a stable FDB dst snapshot in RCU readers

  • 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 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix available
  • 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 “Fix deferred”
  • Red Hat CodeReady Linux Builder EUS (v.9.6) libperf 5.14.0-570.154.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.154.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.154.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.154.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.154.1.el9_6
    fixed: vendor fix RHSA-2026:94438
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.25.1.el9_8, perf 5.14.0-687.25.1.el9_8, rtla 5.14.0-687.25.1.el9_8, python3-perf 5.14.0-687.25.1.el9_8, kernel-devel-matched 5.14.0-687.25.1.el9_8, kernel-64k-devel-matched 5.14.0-687.25.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:38491
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.40.1.el10_2, perf 6.12.0-211.40.1.el10_2, rtla 6.12.0-211.40.1.el10_2, python3-perf 6.12.0-211.40.1.el10_2, kernel-devel-matched 6.12.0-211.40.1.el10_2, kernel-64k-devel-matched 6.12.0-211.40.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:47017
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) rv 5.14.0-427.161.1.el9_4, perf 5.14.0-427.161.1.el9_4, rtla 5.14.0-427.161.1.el9_4, kernel-devel-matched 5.14.0-427.161.1.el9_4, kernel-64k-devel-matched 5.14.0-427.161.1.el9_4, kernel-debug-devel-matched 5.14.0-427.161.1.el9_4, +6 more
    fixed: vendor fix RHSA-2026:94109
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) rv 5.14.0-570.154.1.el9_6, perf 5.14.0-570.154.1.el9_6, rtla 5.14.0-570.154.1.el9_6, python3-perf 5.14.0-570.154.1.el9_6, kernel-devel-matched 5.14.0-570.154.1.el9_6, kernel-64k-devel-matched 5.14.0-570.154.1.el9_6, +7 more
    fixed: vendor fix RHSA-2026:94438
show 22 more
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.144.1.el8_10, kernel 4.18.0-553.144.1.el8_10, bpftool 4.18.0-553.144.1.el8_10, kernel-core 4.18.0-553.144.1.el8_10, kernel-tools 4.18.0-553.144.1.el8_10, python3-perf 4.18.0-553.144.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:39179
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.25.1.el9_8, kernel-64k 5.14.0-687.25.1.el9_8, kernel-core 5.14.0-687.25.1.el9_8, kernel-tools 5.14.0-687.25.1.el9_8, kernel-modules 5.14.0-687.25.1.el9_8, kernel-64k-core 5.14.0-687.25.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:38491
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.40.1.el10_2, kernel-64k 6.12.0-211.40.1.el10_2, kernel-core 6.12.0-211.40.1.el10_2, kernel-tools 6.12.0-211.40.1.el10_2, kernel-modules 6.12.0-211.40.1.el10_2, kernel-64k-core 6.12.0-211.40.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:47017
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) perf 4.18.0-372.225.1.el8_6, kernel 4.18.0-372.225.1.el8_6, bpftool 4.18.0-372.225.1.el8_6, kernel-core 4.18.0-372.225.1.el8_6, kernel-tools 4.18.0-372.225.1.el8_6, python3-perf 4.18.0-372.225.1.el8_6, +8 more
    fixed: vendor fix RHSA-2026:91493
  • Red Hat Enterprise Linux BaseOS E4S (v.8.8) perf 4.18.0-477.177.1.el8_8, kernel 4.18.0-477.177.1.el8_8, bpftool 4.18.0-477.177.1.el8_8, kernel-core 4.18.0-477.177.1.el8_8, kernel-tools 4.18.0-477.177.1.el8_8, python3-perf 4.18.0-477.177.1.el8_8, +9 more
    fixed: vendor fix RHSA-2026:92997
  • Red Hat Enterprise Linux BaseOS E4S (v.9.4) bpftool 7.3.0-427.161.1.el9_4, kernel 5.14.0-427.161.1.el9_4, kernel-64k 5.14.0-427.161.1.el9_4, kernel-core 5.14.0-427.161.1.el9_4, kernel-tools 5.14.0-427.161.1.el9_4, python3-perf 5.14.0-427.161.1.el9_4, +28 more
    fixed: vendor fix RHSA-2026:94109
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) kernel 5.14.0-570.154.1.el9_6, kernel-64k 5.14.0-570.154.1.el9_6, kernel-core 5.14.0-570.154.1.el9_6, kernel-tools 5.14.0-570.154.1.el9_6, kernel-modules 5.14.0-570.154.1.el9_6, kernel-64k-core 5.14.0-570.154.1.el9_6, +27 more
    fixed: vendor fix RHSA-2026:94438
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) perf 4.18.0-372.225.1.el8_6, kernel 4.18.0-372.225.1.el8_6, bpftool 4.18.0-372.225.1.el8_6, kernel-core 4.18.0-372.225.1.el8_6, kernel-tools 4.18.0-372.225.1.el8_6, python3-perf 4.18.0-372.225.1.el8_6, +8 more
    fixed: vendor fix RHSA-2026:91493
  • Red Hat Enterprise Linux BaseOS TUS (v.8.8) perf 4.18.0-477.177.1.el8_8, kernel 4.18.0-477.177.1.el8_8, bpftool 4.18.0-477.177.1.el8_8, kernel-core 4.18.0-477.177.1.el8_8, kernel-tools 4.18.0-477.177.1.el8_8, python3-perf 4.18.0-477.177.1.el8_8, +8 more
    fixed: vendor fix RHSA-2026:92997
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.25.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.25.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.25.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.25.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.25.1.el9_8
    fixed: vendor fix RHSA-2026:38491
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.40.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.40.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.40.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.40.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.40.1.el10_2
    fixed: vendor fix RHSA-2026:47017
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.144.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.144.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.144.1.el8_10
    fixed: vendor fix RHSA-2026:39179
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-kvm 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-core 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-modules 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-debug-kvm 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-debug-core 4.18.0-553.144.1.rt7.485.el8_10, +4 more
    fixed: vendor fix RHSA-2026:39180
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.25.1.el9_8, kernel-rt-64k 5.14.0-687.25.1.el9_8, kernel-rt-core 5.14.0-687.25.1.el9_8, kernel-rt-modules 5.14.0-687.25.1.el9_8, kernel-rt-64k-core 5.14.0-687.25.1.el9_8, kernel-rt-debug-core 5.14.0-687.25.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:38491
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.40.1.el10_2, kernel-rt-64k 6.12.0-211.40.1.el10_2, kernel-rt-core 6.12.0-211.40.1.el10_2, kernel-rt-modules 6.12.0-211.40.1.el10_2, kernel-rt-64k-core 6.12.0-211.40.1.el10_2, kernel-rt-debug-core 6.12.0-211.40.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:47017
  • Red Hat Enterprise Linux Real Time E4S (v.9.4) kernel-rt 5.14.0-427.161.1.el9_4, kernel-rt-core 5.14.0-427.161.1.el9_4, kernel-rt-modules 5.14.0-427.161.1.el9_4, kernel-rt-debug-core 5.14.0-427.161.1.el9_4, kernel-rt-modules-core 5.14.0-427.161.1.el9_4, kernel-rt-debug-modules 5.14.0-427.161.1.el9_4, +4 more
    fixed: vendor fix RHSA-2026:94109
  • Red Hat Enterprise Linux Real Time EUS (v.9.6) kernel-rt 5.14.0-570.154.1.el9_6, kernel-rt-64k 5.14.0-570.154.1.el9_6, kernel-rt-core 5.14.0-570.154.1.el9_6, kernel-rt-modules 5.14.0-570.154.1.el9_6, kernel-rt-64k-core 5.14.0-570.154.1.el9_6, kernel-rt-debug-core 5.14.0-570.154.1.el9_6, +14 more
    fixed: vendor fix RHSA-2026:94438
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.25.1.el9_8, kernel-rt-core 5.14.0-687.25.1.el9_8, kernel-rt-modules 5.14.0-687.25.1.el9_8, kernel-rt-debug-core 5.14.0-687.25.1.el9_8, kernel-rt-modules-core 5.14.0-687.25.1.el9_8, kernel-rt-debug-modules 5.14.0-687.25.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:38491
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.40.1.el10_2, kernel-rt-core 6.12.0-211.40.1.el10_2, kernel-rt-modules 6.12.0-211.40.1.el10_2, kernel-rt-debug-core 6.12.0-211.40.1.el10_2, kernel-rt-modules-core 6.12.0-211.40.1.el10_2, kernel-rt-debug-modules 6.12.0-211.40.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:47017
  • Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4) kernel-rt 5.14.0-427.161.1.el9_4, kernel-rt-kvm 5.14.0-427.161.1.el9_4, kernel-rt-core 5.14.0-427.161.1.el9_4, kernel-rt-modules 5.14.0-427.161.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.161.1.el9_4, kernel-rt-debug-core 5.14.0-427.161.1.el9_4, +6 more
    fixed: vendor fix RHSA-2026:94109
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6) kernel-rt 5.14.0-570.154.1.el9_6, kernel-rt-kvm 5.14.0-570.154.1.el9_6, kernel-rt-core 5.14.0-570.154.1.el9_6, kernel-rt-modules 5.14.0-570.154.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.154.1.el9_6, kernel-rt-debug-core 5.14.0-570.154.1.el9_6, +6 more
    fixed: vendor fix RHSA-2026:94438
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-core 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-modules 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-debug-core 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-debug-modules 4.18.0-553.144.1.rt7.485.el8_10, kernel-rt-modules-extra 4.18.0-553.144.1.rt7.485.el8_10, +2 more
    fixed: vendor fix RHSA-2026:39180

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 0.0

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 ICSA-26-295-16 updated cvss 0.0

Siemens SIMATIC S7-1500 TM MFP

  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
    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
no
Technical impact
partial
Assessed
2 d ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
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
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
  • 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.