CVE-2026-99073

Kernel crash via nexthop-group shrink race

Published Oct 23, 2026 · Updated Oct 23, 2026

Linux IPv4 exception dumps allow local users to crash the kernel through a NULL dereference during nexthop-group replacement. In net/ipv4/route.c, fib_dump_info_fnhe() takes its loop bound from one group snapshot, then dereferences nhc_flags after fib_info_nhc() independently reloads a smaller group and returns NULL. Triggering the race requires concurrent dumping and group replacement with CAP_NET_ADMIN in the relevant network namespace; local users can obtain that capability through new namespaces where unprivileged user namespaces are permitted.

CVSS severityUnavailable
Unscored
EPSS probability0.16%
Next 30 days · Nov 1, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Linux IPv4 exception dumps allow local users to crash the kernel through a NULL dereference during nexthop-group replacement. In net/ipv4/route.c, fib_dump_info_fnhe() takes its loop bound from one group snapshot, then dereferences nhc_flags after fib_info_nhc() independently reloads a smaller group and returns NULL. Triggering the race requires concurrent dumping and group replacement with CAP_NET_ADMIN in the relevant network namespace; local users can obtain that capability through new namespaces where unprivileged user namespaces are permitted.

The record

CVE
CVE-2026-99073
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=4ce5dc9316de50e0da84beafe55d1344f829cece <21cba134c30c17ae55f468b5809336437df5d7e6
  2. Affected versionversion=4ce5dc9316de50e0da84beafe55d1344f829cece <4f4afc07dcb2edd4f9afa36595373f8cdb9b58c2
  3. Affected versionversion=4ce5dc9316de50e0da84beafe55d1344f829cece <b9a30bb7b831e8c5a47fadbdf1760918aaf009cc
  4. Affected versionversion=4ce5dc9316de50e0da84beafe55d1344f829cece <f91e472821e32f58b03eb631e20a67157e2b928b
  5. Affected versionversion=6.9

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4ce5dc9316de50e0da84beafe55d1344f829cece <21cba134c30c17ae55f468b5809336437df5d7e6; version=4ce5dc9316de50e0da84beafe55d1344f829cece <4f4afc07dcb2edd4f9afa36595373f8cdb9b58c2; version=4ce5dc9316de50e0da84beafe55d1344f829cece <b9a30bb7b831e8c5a47fadbdf1760918aaf009cc; version=4ce5dc9316de50e0da84beafe55d1344f829cece <f91e472821e32f58b03eb631e20a67157e2b928b; version=6.9

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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