CVE-2021-47418Public exploit

Kernel crash via missing qdisc change callback

Published May 21, 2024 · Updated May 11, 2026

NULL pointer dereference in the Linux kernel traffic scheduler allows local users to crash the kernel through traffic-control changes. fifo_set_limit() calls the current child qdisc's change operation without confirming that it exists after a TBF child is replaced by pfifo_fast, whose change callback is null. Traffic-control privileges in a network namespace are required; reaching the path dereferences the null callback and stops the kernel.

CVSS severity5.5
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in the Linux kernel traffic scheduler allows local users to crash the kernel through traffic-control changes. fifo_set_limit() calls the current child qdisc's change operation without confirming that it exists after a TBF child is replaced by pfifo_fast, whose change callback is null. Traffic-control privileges in a network namespace are required; reaching the path dereferences the null callback and stops the kernel.

The record

CVE
CVE-2021-47418
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=2.6.27
  2. Affected versionversion=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4
  3. Affected versionversion=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52
  4. Affected versionversion=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <26af64d71b6277841285fa40e3f7164a378dfda9
  5. Affected versionversion=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc
  6. Affected versionversion=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <acff2d182c0768a713cee77442caeb07668bd68f
  7. Affected versionversion=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <c951a3be5e8803e93bb49a0aca0d30457d3c1b67
  8. Affected versionversion=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <d07098f45be868a9cdce6c616563c36c64dbbd87
  9. Affected versionversion=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <fb58cd7991747b5e0b110c98c922d7b0e47a1f14

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.27; version=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4; version=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52; version=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <26af64d71b6277841285fa40e3f7164a378dfda9; version=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc; version=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <acff2d182c0768a713cee77442caeb07668bd68f; version=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <c951a3be5e8803e93bb49a0aca0d30457d3c1b67; version=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <d07098f45be868a9cdce6c616563c36c64dbbd87; version=fb0305ce1b03f6ff17f84f2c63daccecb45f2805 <fb58cd7991747b5e0b110c98c922d7b0e47a1f14

Published CVSS scores

5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS: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 exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

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