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Fencer Vulns
medium 5.5

CVE-2025-21768 json

net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

published 2025-02-27 20 mo ago modified 2026-11-05 3 d ago also EUVD-2025-5155

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 17%
public exploits
0
none known

Summary

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

net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

Some lwtunnels have a dst cache for post-transformation dst. If the packet destination did not change we may end up recording a reference to the lwtunnel in its own cache, and the lwtunnel state will never be freed.

Discovered by the ioam6.sh test, kmemleak was recently fixed to catch per-cpu memory leaks. I'm not sure if rpl and seg6 can actually hit this, but in principle I don't see why not.

Patch / fix

  • Linux Linux 6.1.191, 6.6.160, 6.12.16, 6.13.4, 6.14
  • linux Debian 14, Debian 13 6.12.16-1

debian advisories DEBIAN-CVE-2025-21768

  • linux Ubuntu 24.04 LTS 6.8.0-78.78
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1035.37
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1036.38
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1032.36
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1033.33
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1034.39
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1019.21
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1035.39

ubuntu advisories UBUNTU-CVE-2025-21768

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-rt Real Time Module 15 SP7 6.4.0-150700.7.3.1
  • kernel-syms-rt Real Time Module 15 SP7 6.4.0-150700.7.3.1
  • kernel-rt_debug Real Time Module 15 SP7 6.4.0-150700.7.3.1
  • kernel-source-rt Real Time Module 15 SP7 6.4.0-150700.7.3.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-syms-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-source-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.3.1
  • kernel-rt Real Time Module 15 SP6, openSUSE Leap 15.6 6.4.0-150600.10.39.1

suse advisories SUSE-SU-2025:01972-1SUSE-SU-2025:01967-1SUSE-SU-2025:01964-1SUSE-SU-2025:01951-1SUSE-SU-2025:01919-1SUSE-SU-2025:01707-1

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-2025-21768 updated cvss 5.5

kernel: net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
    affected: no fix available
  • Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more 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
no
Technical impact
partial
Assessed
3 d ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 17% 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

Classification

Weakness
  • CWE-401 Missing Release of Memory after Effective Lifetime
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.