CVE-2026-63968: Linux kernel · ipv6: fix possible infinite loop in fib6_select_path()
Affects Linux kernelSource CVE Database V5
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
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| 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
- git.kernel.org/stable/c/3948a7d92f7678e89e1776bb2d169afcad63b1ae (opens in a new tab)
- git.kernel.org/stable/c/c87cd3cb309634bc8f50a54e2079424f219ac21f (opens in a new tab)
- git.kernel.org/stable/c/0f7b73c3452635de83b8711b31abdda8e49aad7b (opens in a new tab)
- git.kernel.org/stable/c/ab9a10969a907b472a0196d999c08ff7144172e3 (opens in a new tab)
- git.kernel.org/stable/c/9b9d5bd6e3d4c9cecab5407604b690684b2532d2 (opens in a new tab)
- git.kernel.org/stable/c/9c7da87c2dc860bb17ca1ece942495d28b1ce3b9 (opens in a new tab)