VulnerabilityPublished 26 Oct 2026Updated 27 Oct 2026

CVE-2026-99073: Linux kernel · ipv4: stop exception dump when nexthop group shrinks

Affects Linux kernelSource GCVE Database

Authoritative record:CVE-2026-99073· 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 prevents the exception by stopping the walk when the indexed path is absent. Users should apply the updated Linux kernel versions that include this fix to mitigate the vulnerability.

Description

A vulnerability in the Linux kernel IPv4 implementation could cause an exception dump when a nexthop group shrinks during concurrent routing table dumps. This occurs due to a race condition where the nexthop group size changes between two related function calls, leading to a NULL pointer dereference. The issue has been resolved by stopping the walk when the indexed path is absent.

Impact

This flaw can cause an exception dump (kernel crash or instability) in the IPv4 routing subsystem of the Linux kernel when nexthop groups shrink during concurrent routing table dumps. This could lead to denial of service by crashing or destabilizing the kernel.

Summary

The vulnerability arises from commit 4ce5dc9316de that allowed concurrent IPv4 FIB dumps with nexthop replacements. Specifically, fib_dump_info_fnhe() uses fib_info_num_path() as a loop bound, but fib_info_nhc() reloads nh->nh_grp independently. If RTM_NEWNEXTHOP replaces a group with fewer paths between these calls, fib_info_nhc() returns NULL, and the subsequent dereference of nhc_flags causes an exception dump. The fix stops the walk when the indexed path is absent, preventing the NULL dereference.

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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