VulnerabilityPublished 26 Oct 2026Updated 27 Oct 2026

CVE-2026-99072: Linux kernel · ipv4: stop route notification sizing when nexthop group shrinks

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-99072· Medium

Not known to be exploited.

Data as of 28 Oct 2026, 01:31 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Oct 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

Affected software

Product	Affected	Fixed in
Ubuntu 26.10linux`pkg:deb/ubuntu/linux?arch=source&distro=stonking`Other threats	Affected 7.0.0-14.14 – 7.3.0-9.9 6 affected builds	Fixed in–
Ubuntu 26.10linux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=stonking`Other threats	Affected 7.0.0-1004.4 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonking`Other threats	Affected =7.0.0-1004.4 =7.3.0-1002.3 =7.3.0-1003.4	Fixed in–
Ubuntu 26.10linux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=stonking`Other threats	Affected 7.0.0-1003.3 – 7.3.0-1003.3 5 affected builds	Fixed in–
Ubuntu 26.10linux-oracle`pkg:deb/ubuntu/linux-oracle?arch=source&distro=stonking`Other threats	Affected 7.0.0-1003.3 – 7.3.0-1003.3 5 affected builds	Fixed in–

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

AI-suggested

A fix is available that stops the route notification sizing when the nexthop group shrinks, preventing the null pointer dereference. Users should apply the updated kernel versions that include this fix. No additional mitigation steps are indicated.

Description

A vulnerability in the Linux kernel's IPv4 routing notification mechanism could cause a null pointer dereference when a nexthop group shrinks during route notification sizing. This occurs because the code does not properly handle the case where the nexthop group has fewer paths after an update, leading to a potential crash or instability. The issue has been resolved by stopping the sizing process when the indexed path is absent.

Impact

This vulnerability can lead to a kernel null pointer dereference, which may cause system instability or crashes. There is no indication of remote code execution or privilege escalation. The impact is limited to denial of service or system disruption due to kernel faults.

Summary

The vulnerability in the Linux kernel involves the IPv4 route notification sizing logic when a nexthop group shrinks. Specifically, the function fib_nlmsg_size() checks the number of paths before iterating, but fib_info_nhc() reloads the nexthop group independently. If the nexthop group is replaced with fewer paths between these calls, fib_info_nhc() returns NULL, causing fib_nexthop_nlmsg_size() to dereference a NULL pointer. The fix prevents sizing when the indexed path is missing, avoiding the null pointer dereference and potential kernel crash.

GCVE source: db.gcve.eu
OSV ID: UBUNTU-CVE-2026-99072
Osv Schema Version: 1.7.0
Ecosystems: Ubuntu:16.04:LTS, Ubuntu:18.04:LTS, Ubuntu:20.04:LTS, Ubuntu:Pro:20.04:LTS, Ubuntu:22.04:LTS, Ubuntu:Nvidia-BlueField:22.04:LTS, Ubuntu:Pro:Realtime:22.04:LTS, Ubuntu:Pro:FIPS-preview:22.04:LTS, Ubuntu:Pro:FIPS-updates:22.04:LTS, Ubuntu:24.04:LTS, Ubuntu:Nvidia-BlueField:24.04:LTS, Ubuntu:Pro:Realtime:24.04:LTS, Ubuntu:Pro:FIPS-updates:24.04:LTS, Ubuntu:26.10, Ubuntu:26.04:LTS

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Oct 2026, 01:31 UTC

Technical details

References

Community reviews

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