CVE-2021-4002Public exploit

Cross-process data access via missing TLB flush

Published Mar 3, 2022 · Updated Aug 3, 2024

Memory corruption in Linux Kernel 3.6 through 5.15.5 allows local users to read or alter huge-page data from other processes. The hugetlb unmapping path clears a shared PUD without flushing the corresponding TLB entries, leaving stale translations to pages reallocated to another process. Exploitation requires local code execution, PUD-aligned shared huge-page mappings, available huge pages, and timely page reuse.

CVSS severity4.4
Medium
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Linux Kernel 3.6 through 5.15.5 allows local users to read or alter huge-page data from other processes. The hugetlb unmapping path clears a shared PUD without flushing the corresponding TLB entries, leaving stale translations to pages reallocated to another process. Exploitation requires local code execution, PUD-aligned shared huge-page mappings, available huge pages, and timely page reuse.

The record

CVE
CVE-2021-4002
Published
Mar 3, 2022
Updated
Aug 3, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-401, CWE-459
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 3, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=affects kernel v3.6 and later through v5.15.5.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=affects kernel v3.6 and later through v5.15.5.

Published CVSS scores

3.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:N
4.4Oracle LinuxCVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
4.4NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

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 exploitPublished

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
CWE-459Incomplete Cleanup

Public exploit references

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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