VulnerabilityPublished 20 Jul 2026Updated 9 Oct 2026

CVE-2026-63969: Linux kernel · ipv6: fix possible infinite loop in rt6_fill_node()

Affects Linux kernelSource GCVE Database

Not known to be exploited · fixed in 6.8.0-1066.69~22.04.1 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 12:55 UTC

Severity

Medium

Rated by Threat Radar · No CVSS score from NVD or the CNA

EPSS: 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 6.8.0-1066.69~22.04.1, 6.8.0-1070.78~22.04.1, 6.8.0-1068.75~22.04.1 +36

Exploitation evidence

Disclosed: evidence found.
CVE published 20 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected <7.0.0-28.28	Fixed in 7.0.0-28.28
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected <7.0.0-1009.9	Fixed in 7.0.0-1009.9
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected <7.0.0-1010.10	Fixed in 7.0.0-1010.10
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected <7.0.0-1009.9	Fixed in 7.0.0-1009.9
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected <7.0.0-1008.8	Fixed in 7.0.0-1008.8
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected <7.0.0-1003.4	Fixed in 7.0.0-1003.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

An official fix is available and should be applied. The vulnerability has been resolved in updated Linux kernel versions. Users should update to the fixed kernel releases as provided by their Linux distribution vendors. No additional mitigation steps are required beyond applying the patch.

Description

A vulnerability in the Linux kernel's IPv6 implementation could cause a possible infinite loop in the rt6_fill_node() function, leading to a CPU stall. This issue arises from improper handling of linked list pointers during route deletion under certain locking conditions. The flaw has been fixed by applying a patch that ensures reliable detachment signals to prevent the infinite loop.

Impact

The vulnerability can cause a CPU stall due to an infinite loop in the IPv6 routing code, potentially impacting system stability and availability. There is no indication of privilege escalation or data compromise from this issue alone.

Summary

The Linux kernel contained a vulnerability in the IPv6 subsystem where the rt6_fill_node() function could enter an infinite loop due to improper synchronization when deleting routes. Specifically, writers holding the tb6_lock could call list_del_rcu(&rt->fib6_siblings) without waiting for RCU readers, leaving the rt->fib6_siblings.next pointer referencing an old ring. This caused a softirq-side walker to never reach &rt->fib6_siblings, resulting in a CPU stall. The fix applies the same approach as a previous patch (commit f8d8ce1b515a) by using fib6_del_route() to WRITE_ONCE() rt->fib6_nsiblings to 0 before list_del_rcu(), providing a reliable detach signal inside the loop. The vulnerability was reported by Sashiko and is tracked as CVE-2026-63969.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Oct 2026, 12:59 UTC

Technical details

References

Community reviews

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