CVE-2026-99074

Kernel crash via nexthop-group shrink race

Published Oct 23, 2026 · Updated Oct 23, 2026

A race in Linux IPv4 PMTU updates allows local users to crash the kernel through concurrent nexthop-group replacement. In __ip_rt_update_pmtu(), separate group reads can accept an index from a larger group and then pass a NULL path to update_or_create_fnhe(), which dereferences it. Replacement requires CAP_NET_ADMIN in the network namespace; local users can obtain that capability through new user and network namespaces where unprivileged user namespaces are permitted.

CVSS severityUnavailable
Unscored
EPSS probability0.15%
Next 30 days · Nov 1, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A race in Linux IPv4 PMTU updates allows local users to crash the kernel through concurrent nexthop-group replacement. In __ip_rt_update_pmtu(), separate group reads can accept an index from a larger group and then pass a NULL path to update_or_create_fnhe(), which dereferences it. Replacement requires CAP_NET_ADMIN in the network namespace; local users can obtain that capability through new user and network namespaces where unprivileged user namespaces are permitted.

The record

CVE
CVE-2026-99074
Published
Oct 23, 2026
Updated
Oct 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 23, 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=3bed2abab4a682d426624ce9add9d7b6d475d4e4 <7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a
  2. Affected versionversion=5.15.179 <5.16
  3. Affected versionversion=6.1.129 <6.2
  4. Affected versionversion=6.12.16 <6.12.113
  5. Affected versionversion=6.13
  6. Affected versionversion=6.6.79 <6.6.160
  7. Affected versionversion=7d3f3b4367f315a61fc615e3138f3d320da8c466 <6619e01855e65ef35723685a557e3eb106f4ecf5
  8. Affected versionversion=7d3f3b4367f315a61fc615e3138f3d320da8c466 <c6d670ac656badfd0e15355e07a13a6bdf3b69fd
  9. Affected versionversion=7d3f3b4367f315a61fc615e3138f3d320da8c466 <f27483f9975b5065ff67054cc7eb8edac6083488
  10. Affected versionversion=7f5005457b3072fe1ddf15bfef869f2a1d98e05e <c60d17d6dd61adc761ac6f65a008fefbc54cbf87
  11. Affected versionversion=b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e
  12. Affected versionversion=fc07a232326a623d0be482e307c08ea7049c2846

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3bed2abab4a682d426624ce9add9d7b6d475d4e4 <7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a; version=5.15.179 <5.16; version=6.1.129 <6.2; version=6.12.16 <6.12.113; version=6.13; version=6.6.79 <6.6.160; version=7d3f3b4367f315a61fc615e3138f3d320da8c466 <6619e01855e65ef35723685a557e3eb106f4ecf5; version=7d3f3b4367f315a61fc615e3138f3d320da8c466 <c6d670ac656badfd0e15355e07a13a6bdf3b69fd; version=7d3f3b4367f315a61fc615e3138f3d320da8c466 <f27483f9975b5065ff67054cc7eb8edac6083488; version=7f5005457b3072fe1ddf15bfef869f2a1d98e05e <c60d17d6dd61adc761ac6f65a008fefbc54cbf87; version=b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e; version=fc07a232326a623d0be482e307c08ea7049c2846

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

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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