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Fencer Vulns
high 7.5

CVE-2025-40183 json

bpf: Fix metadata_dst leak __bpf_redirect_neigh_v{4,6}

published 2025-11-12 11 mo ago modified 2026-10-19 20 d ago also EUVD-2025-150391

cvss
7.5
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:

bpf: Fix metadata_dst leak __bpf_redirect_neigh_v{4,6}

Cilium has a BPF egress gateway feature which forces outgoing K8s Pod traffic to pass through dedicated egress gateways which then SNAT the traffic in order to interact with stable IPs outside the cluster.

The traffic is directed to the gateway via vxlan tunnel in collect md mode. A recent BPF change utilized the bpf_redirect_neigh() helper to forward packets after the arrival and decap on vxlan, which turned out over time that the kmalloc-256 slab usage in kernel was ever-increasing.

The issue was that vxlan allocates the metadata_dst object and attaches it through a fake dst entry to the skb. The latter was never released though given bpf_redirect_neigh() was merely setting the new dst entry via skb_dst_set() without dropping an existing one first.

Patch / fix

  • Linux Linux 5.10.246, 5.15.195, 6.1.157, 6.6.113, 6.12.54, 6.17.4, 6.18
  • linux Debian 12 6.1.158-1
  • linux Debian 13 6.12.57-1
  • linux Debian 14 6.17.6-1

debian advisories DEBIAN-CVE-2025-40183

  • linux Ubuntu 22.04 LTS 5.15.0-170.180
  • linux Ubuntu 24.04 LTS 6.8.0-106.106
  • linux Ubuntu 25.10 6.17.0-14.14
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1100.107
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1050.53
  • linux-aws Ubuntu 25.10 6.17.0-1007.7
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1100.109
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1052.55

ubuntu advisories UBUNTU-CVE-2025-40183

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-source Linux Micro 6.1, Linux Micro 6.0 6.4.0-38.1
  • kernel-default Linux Micro 6.1, Linux Micro 6.0 6.4.0-38.1
  • kernel-kvmsmall Linux Micro 6.1, Linux Micro 6.0 6.4.0-38.1
  • kernel-default-base Linux Micro 6.1, Linux Micro 6.0 6.4.0-38.1.21.15
  • kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-39.1
  • kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-39.1
  • kernel-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.61.1
  • kernel-syms-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.61.1

suse advisories SUSE-SU-2026:20473-1SUSE-SU-2026:20496-1SUSE-SU-2026:20039-1SUSE-SU-2026:20059-1SUSE-SU-2025:4521-1SUSE-SU-2025:4517-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.8.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-kvmsmall openSUSE Leap 16.0 6.12.0-160000.8.1

opensuse advisories openSUSE-SU-2025:20172-1

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-2025-40183 updated cvss 4.4

kernel: bpf: Fix metadata_dst leak __bpf_redirect_neigh_v{4,6}

  • 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 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 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
partial
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 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

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.