Remote denial of service via stale sibling traversal
Published Jul 19, 2026 · Updated Jul 19, 2026
A race in IPv6 route selection in Linux Kernel allows remote attackers to hang or panic systems through IPv6 traffic during route churn. fib6_select_path() follows first->fib6_siblings.next after a writer removes the sibling under tb6_lock, so the RCU reader circles the detached ring instead of reaching its terminator. Exploitation requires traffic through a vulnerable multipath route while a concurrent route-table update occurs; the resulting softirq loop can stall a CPU and end in a watchdog-triggered kernel panic.
Summary
What happened
A race in IPv6 route selection in Linux Kernel allows remote attackers to hang or panic systems through IPv6 traffic during route churn. fib6_select_path() follows first->fib6_siblings.next after a writer removes the sibling under tb6_lock, so the RCU reader circles the detached ring instead of reaching its terminator. Exploitation requires traffic through a vulnerable multipath route while a concurrent route-table update occurs; the resulting softirq loop can stall a CPU and end in a watchdog-triggered kernel panic.
The record
- CVE
- CVE-2026-63968
- Published
- Jul 19, 2026
- Updated
- Jul 19, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 19, 2026CVE publishedPublication date reported by the CVE source.
- Jul 19, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=11edcd026012ac18acee0f1514db3ed1b160fc6f
- Affected versionversion=34a949e7a0869dfa31a40416d2a56973fae1807b <0f7b73c3452635de83b8711b31abdda8e49aad7b
- Affected versionversion=52da02521ede55fb86546c3fffd9377b3261b91f <c87cd3cb309634bc8f50a54e2079424f219ac21f
- Affected versionversion=6.11.11 <6.12
- Affected versionversion=6.1.128 <6.1.176
- Affected versionversion=6.12.2 <6.12.93
- Affected versionversion=6.13
- Affected versionversion=6.6.75 <6.6.143
- Affected versionversion=d0ec61c9f3583b76aebdbb271f5c0d3fcccd48b2 <3948a7d92f7678e89e1776bb2d169afcad63b1ae
- Affected versionversion=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <9b9d5bd6e3d4c9cecab5407604b690684b2532d2
- Affected versionversion=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <9c7da87c2dc860bb17ca1ece942495d28b1ce3b9
- Affected versionversion=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <ab9a10969a907b472a0196d999c08ff7144172e3
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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