CVE-2021-47129

Local service interruption via confirmed conntrack extension

Published Mar 15, 2024 · Updated Aug 5, 2026

Improper input validation in Linux kernel nft_ct allows local users to interrupt service through crafted conntrack expectations. nft_ct_expect_obj_eval() incorrectly calls nf_ct_ext_add() on a confirmed conntrack entry even though extensions can be added only before confirmation. Exploitation requires local low-privileged access and evaluation of nftables connection-tracking expectations, with availability impact only under Red Hat's assessment.

CVSS severity7.8
High
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Linux kernel nft_ct allows local users to interrupt service through crafted conntrack expectations. nft_ct_expect_obj_eval() incorrectly calls nf_ct_ext_add() on a confirmed conntrack entry even though extensions can be added only before confirmation. Exploitation requires local low-privileged access and evaluation of nftables connection-tracking expectations, with availability impact only under Red Hat's assessment.

The record

CVE
CVE-2021-47129
Published
Mar 15, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-20
Attack vector
local
Privileges
authenticated

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=5.3
  2. Affected versionversion=857b46027d6f91150797295752581b7155b9d0e1 <1710eb913bdcda3917f44d383c32de6bdabfc836
  3. Affected versionversion=857b46027d6f91150797295752581b7155b9d0e1 <2c0e6b35b88a961127066a1028bce9c727cbc3e5
  4. Affected versionversion=857b46027d6f91150797295752581b7155b9d0e1 <5f3429c05e4028a0e241afdad856dd15dec2ffb9
  5. Affected versionversion=857b46027d6f91150797295752581b7155b9d0e1 <da8d31e80ff425f5a65dab7060d5c4aba749e562

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.3; version=857b46027d6f91150797295752581b7155b9d0e1 <1710eb913bdcda3917f44d383c32de6bdabfc836; version=857b46027d6f91150797295752581b7155b9d0e1 <2c0e6b35b88a961127066a1028bce9c727cbc3e5; version=857b46027d6f91150797295752581b7155b9d0e1 <5f3429c05e4028a0e241afdad856dd15dec2ffb9; version=857b46027d6f91150797295752581b7155b9d0e1 <da8d31e80ff425f5a65dab7060d5c4aba749e562

Published CVSS scores

7.8CVE.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation

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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