CVE-2021-47400

Kernel crash via repeated hns3 network opening

Published May 21, 2024 · Updated Aug 5, 2026

Denial of service in affected Linux kernel releases allows local users to crash the kernel through concurrent hns3 reset and tc setup. A race can invoke hns3_nic_net_open() twice because it fails to test the cleared HNS3_NIC_STATE_DOWN flag, causing napi_enable() to run twice and hit a kernel BUG. Reaching the race requires an hns3 network device and overlapping device-reset and traffic-control setup operations; the documented consequence is a kernel crash.

CVSS severity5.5
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Linux kernel releases allows local users to crash the kernel through concurrent hns3 reset and tc setup. A race can invoke hns3_nic_net_open() twice because it fails to test the cleared HNS3_NIC_STATE_DOWN flag, causing napi_enable() to run twice and hit a kernel BUG. Reaching the race requires an hns3 network device and overlapping device-reset and traffic-control setup operations; the documented consequence is a kernel crash.

The record

CVE
CVE-2021-47400
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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=e888402789b9db5de4fcda361331d66dbf0cd9fd <3dac38bdce7932901b9f0b71c62331852c809e61
  3. Affected versionversion=e888402789b9db5de4fcda361331d66dbf0cd9fd <5a31d4e73ada8022427b69b10fd1f01a6a8d4b3d
  4. Affected versionversion=e888402789b9db5de4fcda361331d66dbf0cd9fd <5b09e88e1bf7fe86540fab4b5f3eece8abead39e
  5. Affected versionversion=e888402789b9db5de4fcda361331d66dbf0cd9fd <f8ba689cb69523144d10606096ef686002dd7285

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.0; version=e888402789b9db5de4fcda361331d66dbf0cd9fd <3dac38bdce7932901b9f0b71c62331852c809e61; version=e888402789b9db5de4fcda361331d66dbf0cd9fd <5a31d4e73ada8022427b69b10fd1f01a6a8d4b3d; version=e888402789b9db5de4fcda361331d66dbf0cd9fd <5b09e88e1bf7fe86540fab4b5f3eece8abead39e; version=e888402789b9db5de4fcda361331d66dbf0cd9fd <f8ba689cb69523144d10606096ef686002dd7285

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0CISA ADPCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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

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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