CVE-2026-63969

Local denial of service via route-sibling race

Published Jul 19, 2026 · Updated Jul 19, 2026

Denial of service in the Linux kernel IPv6 subsystem allows local users to stall a CPU by triggering rt6_fill_node(). While tb6_lock writers remove a route from fib6_siblings with list_del_rcu(), an RCU reader follows the stale next pointer around the old ring without reaching its terminator. Local low-privileged access is required, and the resulting infinite softirq loop consumes a CPU and can interrupt system availability.

CVSS severity5.5
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the Linux kernel IPv6 subsystem allows local users to stall a CPU by triggering rt6_fill_node(). While tb6_lock writers remove a route from fib6_siblings with list_del_rcu(), an RCU reader follows the stale next pointer around the old ring without reaching its terminator. Local low-privileged access is required, and the resulting infinite softirq loop consumes a CPU and can interrupt system availability.

The record

CVE
CVE-2026-63969
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-835, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. 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.

  1. Affected versionversion=11edcd026012ac18acee0f1514db3ed1b160fc6f
  2. Affected versionversion=34a949e7a0869dfa31a40416d2a56973fae1807b <c65b1f60237daac7c56c2652e064cc566a45dc81
  3. Affected versionversion=52da02521ede55fb86546c3fffd9377b3261b91f <279853aec9f58d5cd723e6e5617c1c3337b30383
  4. Affected versionversion=6.11.11 <6.12
  5. Affected versionversion=6.1.128 <6.1.176
  6. Affected versionversion=6.12.2 <6.12.93
  7. Affected versionversion=6.13
  8. Affected versionversion=6.6.75 <6.6.143
  9. Affected versionversion=d0ec61c9f3583b76aebdbb271f5c0d3fcccd48b2 <b014a63d2f2c2c767762b548381882dfb1655529
  10. Affected versionversion=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <5e40de719ee76b8d96e2556ce36dbd3bd07bf37d
  11. Affected versionversion=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <9f72412bcf60144f252b0d6205106abf14344abc
  12. Affected versionversion=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <dc36a04621dcc2447dae428709207810b6c06e14

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=11edcd026012ac18acee0f1514db3ed1b160fc6f; version=34a949e7a0869dfa31a40416d2a56973fae1807b <c65b1f60237daac7c56c2652e064cc566a45dc81; version=52da02521ede55fb86546c3fffd9377b3261b91f <279853aec9f58d5cd723e6e5617c1c3337b30383; version=6.11.11 <6.12; version=6.1.128 <6.1.176; version=6.12.2 <6.12.93; version=6.13; version=6.6.75 <6.6.143; version=d0ec61c9f3583b76aebdbb271f5c0d3fcccd48b2 <b014a63d2f2c2c767762b548381882dfb1655529; version=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <5e40de719ee76b8d96e2556ce36dbd3bd07bf37d; version=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <9f72412bcf60144f252b0d6205106abf14344abc; version=d9ccb18f83ea2bb654289b6ecf014fd267cc988b <dc36a04621dcc2447dae428709207810b6c06e14

Published CVSS scores

5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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