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Fencer Intel
high 7.5

CVE-2026-63968 json

ipv6: fix possible infinite loop in fib6_select_path()

published 3mo ago modified 12d ago also EUVD-2026-45741

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 52%
public exploits
0
none known

Summary

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

ipv6: fix possible infinite loop in fib6_select_path()

Found while auditing the same pattern Sashiko reported in rt6_fill_node() [1]. Apply the same fix as commit f8d8ce1b515a ("ipv6: fix possible infinite loop in fib6_info_uses_dev()").

Writers holding tb6_lock can list_del_rcu(&first->fib6_siblings) without waiting for RCU readers; first->fib6_siblings.next then still points into the old ring and this softirq-side walker never reaches &first->fib6_siblings as its terminator. fib6_purge_rt() always WRITE_ONCE()s first->fib6_nsiblings to 0 before list_del_rcu(), so an inside-loop check is a reliable detach signal.

[1] https://sashiko.dev/#/patchset/20260526020227.4857-1-jiayuan.chen%40linux.dev

Patch / fix

  • Linux Linux 6.1.176, 6.6.143, 6.12, 6.12.93, 6.18.35, 7.0.12, 7.1
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-63968

  • linux Ubuntu 24.04 LTS 6.8.0-146.146
  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1066.69
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1070.78
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1008.8
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1065.73
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1003.4

ubuntu advisories UBUNTU-CVE-2026-63968

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-livepatch-SLE16-RT_Update_5 Linux Micro 6.2 14-160000.1.1
  • kernel-livepatch-SLE16-RT_Update_3 Linux Micro 6.2 15-160000.1.1
  • kernel-livepatch-SLE16-RT_Update_2 Linux Micro 6.2 16-160000.1.1
  • kernel-livepatch-SLE16-RT_Update_1 Linux Micro 6.2 18-160000.1.1
  • kernel-livepatch-SLE16-RT_Update_0 Linux Micro 6.2 19-160000.3.4
  • kernel-livepatch-SLE16-RT_Update_12 Linux Micro 6.2 8-160000.1.1
  • kernel-livepatch-SLE16-RT_Update_11 Linux Micro 6.2 10-160000.1.1
  • kernel-livepatch-SLE16-RT_Update_10 Linux Micro 6.2 10-160000.1.1

suse advisories SUSE-SU-2026:5059-1SUSE-SU-2026:5053-1SUSE-SU-2026:24534-1SUSE-SU-2026:24535-1SUSE-SU-2026:24536-1SUSE-SU-2026:24537-1

  • 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

Is CVE-2026-63968 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2026-63968 updated cvss 5.1

kernel: ipv6: fix possible infinite loop in fib6_select_path()

  • 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 rv, perf, rtla, kernel, bpftool, libperf, +82 more Red Hat Enterprise Linux 10 kernel
    affected: workaround, no fix available
  • 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 Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-selftests-internal
    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
26d ago

Exploit prediction

0.67% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-11).

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

Weakness
  • CWE-835 Loop with Unreachable Exit Condition
Technology feeds

References

Sources

Fencer Intel 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.