CVE-2021-47430

Kernel warning via stale SMAP capability state

Published May 21, 2024 · Updated May 11, 2026

Improper x86 SMAP state handling in Linux before 5.15 allows local users to trigger a kernel warning through a crafted syscall. The x86 CPU setup path retains X86_FEATURE_SMAP from hardware when CONFIG_X86_SMAP is disabled, so entry code applies an AC-flag assertion for an inactive feature. Exploitation requires an SMAP-capable x86 processor and an affected build configuration; the reported consequence is a warning and diagnostic trace, not data access or code execution.

CVSS severity3.3
Low
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper x86 SMAP state handling in Linux before 5.15 allows local users to trigger a kernel warning through a crafted syscall. The x86 CPU setup path retains X86_FEATURE_SMAP from hardware when CONFIG_X86_SMAP is disabled, so entry code applies an AC-flag assertion for an inactive feature. Exploitation requires an SMAP-capable x86 processor and an affected build configuration; the reported consequence is a warning and diagnostic trace, not data access or code execution.

The record

CVE
CVE-2021-47430
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3c73b81a9164d0c1b6379d6672d2772a9e95168e <3958b9c34c2729597e182cc606cc43942fd19f7c
  2. Affected versionversion=3c73b81a9164d0c1b6379d6672d2772a9e95168e <4e9ec1c65da98c293f75d83755dfa5e03075a6d0
  3. Affected versionversion=3c73b81a9164d0c1b6379d6672d2772a9e95168e <f2447f6587b8ffe42ba04d14ce67d429a1163e5e
  4. Affected versionversion=5.8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3c73b81a9164d0c1b6379d6672d2772a9e95168e <3958b9c34c2729597e182cc606cc43942fd19f7c; version=3c73b81a9164d0c1b6379d6672d2772a9e95168e <4e9ec1c65da98c293f75d83755dfa5e03075a6d0; version=3c73b81a9164d0c1b6379d6672d2772a9e95168e <f2447f6587b8ffe42ba04d14ce67d429a1163e5e; version=5.8

Published CVSS scores

3.3UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
3.3NISTCVSS:3.1/AV:L/AC:L/PR:L/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

No sourced classifications are available.

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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