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VulnerabilityPublished Updated

CVE-2026-63968: Linux kernel · ipv6: fix possible infinite loop in fib6_select_path()

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.5 High · fixed in c87cd3cb309634bc8f50a54e2079424f219ac21f : patch Linux kernel soon.

Data as of 26 Oct 2026, 10:24 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 51% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers can reliably automate steps 1–4 of the kill chain
Technical impact
Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in c87cd3cb309634bc8f50a54e2079424f219ac21f, ab9a10969a907b472a0196d999c08ff7144172e3, 3948a7d92f7678e89e1776bb2d169afcad63b1ae +7
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • >=6.1.128 <6.1.176
  • >=6.6.75 <6.6.143
  • >=6.12.2 <6.12.93
  • >=6.11.11 <6.12
Fixed in
  • c87cd3cb309634bc8f50a54e2079424f219ac21f
  • ab9a10969a907b472a0196d999c08ff7144172e3
  • 3948a7d92f7678e89e1776bb2d169afcad63b1ae
  • 9c7da87c2dc860bb17ca1ece942495d28b1ce3b9
  • 9b9d5bd6e3d4c9cecab5407604b690684b2532d2
  • 6.12.93
  • 6.12
  • 6.6.143
  • 6.1.176
  • 0f7b73c3452635de83b8711b31abdda8e49aad7b
LinuxLinuxAffected
  • =6.13
Fixed in–

Description

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

References

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