CVE-2021-47109Network attack vector

Unauthenticated IPv6 disruption via persistent neighbor entries

Published Mar 15, 2024 · Updated Aug 5, 2026

Resource exhaustion in the Linux kernel allows remote attackers to disrupt valid IPv6 point-to-point connections. The neighbor-table garbage collector in net/core/neighbour.c retains NUD_NOARP entries unless they are failed or older than five seconds, allowing repeated entries to consume the table. Exploitation requires IPv6 on an IFF_POINTOPOINT interface and enough crafted neighbor entries; the documented consequence is loss of valid connections.

CVSS severity7.5
High
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in the Linux kernel allows remote attackers to disrupt valid IPv6 point-to-point connections. The neighbor-table garbage collector in net/core/neighbour.c retains NUD_NOARP entries unless they are failed or older than five seconds, allowing repeated entries to consume the table. Exploitation requires IPv6 on an IFF_POINTOPOINT interface and enough crafted neighbor entries; the documented consequence is loss of valid connections.

The record

CVE
CVE-2021-47109
Published
Mar 15, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-190, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 15, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=5.0
  2. Affected versionversion=58956317c8de52009d1a38a721474c24aef74fe7 <7a6b1ab7475fd6478eeaf5c9d1163e7a18125c8f
  3. Affected versionversion=58956317c8de52009d1a38a721474c24aef74fe7 <d17d47da59f726dc4c87caebda3a50333d7e2fd3
  4. Affected versionversion=58956317c8de52009d1a38a721474c24aef74fe7 <d99029e6aab62aef0a0251588b2867e77e83b137
  5. Affected versionversion=58956317c8de52009d1a38a721474c24aef74fe7 <ddf088d7aaaaacfc836104f2e632b29b1d383cfc

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.0; version=58956317c8de52009d1a38a721474c24aef74fe7 <7a6b1ab7475fd6478eeaf5c9d1163e7a18125c8f; version=58956317c8de52009d1a38a721474c24aef74fe7 <d17d47da59f726dc4c87caebda3a50333d7e2fd3; version=58956317c8de52009d1a38a721474c24aef74fe7 <d99029e6aab62aef0a0251588b2867e77e83b137; version=58956317c8de52009d1a38a721474c24aef74fe7 <ddf088d7aaaaacfc836104f2e632b29b1d383cfc

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.5kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
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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