CVE-2021-28971Public exploit

System crash via uncleared zero PEBS status

Published Mar 22, 2021 · Updated Aug 3, 2024

Denial of service in the Linux kernel through 5.11.8 allows local users on some Haswell CPUs to crash the system via PEBS sampling. The intel_pmu_drain_pebs_nhm function repairs a zero PEBS status only in its local variable, leaving the record unchanged; a later large-PEBS lookup receives NULL and dereferences it. Exploitation requires local access to performance counters on an affected Haswell system and interrupts the entire system without reported confidentiality or integrity impact.

CVSS severity5.5
Medium
EPSS probability0.39%
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 the Linux kernel through 5.11.8 allows local users on some Haswell CPUs to crash the system via PEBS sampling. The intel_pmu_drain_pebs_nhm function repairs a zero PEBS status only in its local variable, leaving the record unchanged; a later large-PEBS lookup receives NULL and dereferences it. Exploitation requires local access to performance counters on an affected Haswell system and interrupts the entire system without reported confidentiality or integrity impact.

The record

CVE
CVE-2021-28971
Published
Mar 22, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-755, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 22, 2021CVE 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.9NIST NVDAV:L/AC:L/Au:N/C:N/I:N/A:C

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-755Improper Handling of Exceptional Conditions
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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