CVE-2021-47044

Kernel disclosure and crash via uncapped shift

Published Feb 28, 2024 · Updated May 11, 2026

Undefined behavior in the Linux kernel scheduler allows local users to disclose kernel data or crash an affected Linux system. In load_balance(), repeated failures can grow nr_balance_failed until it supplies an oversized exponent to a shift operation. The path requires a selected task that cannot run on the destination CPU, after which continued failures leave the counter uncapped.

CVSS severity7.7
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Undefined behavior in the Linux kernel scheduler allows local users to disclose kernel data or crash an affected Linux system. In load_balance(), repeated failures can grow nr_balance_failed until it supplies an oversized exponent to a shift operation. The path requires a selected task that cannot run on the destination CPU, after which continued failures leave the counter uncapped.

The record

CVE
CVE-2021-47044
Published
Feb 28, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125, T1499
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 28, 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=5.10
  2. Affected versionversion=5a7f555904671c0737819fe4d19bd6143de3f6c0 <2f3eab368e313dba35fc2f51ede778bf7b030b54
  3. Affected versionversion=5a7f555904671c0737819fe4d19bd6143de3f6c0 <39a2a6eb5c9b66ea7c8055026303b3aa681b49a5
  4. Affected versionversion=5a7f555904671c0737819fe4d19bd6143de3f6c0 <805cea93e66ca7deaaf6ad3b67224ce47c104c2f
  5. Affected versionversion=5a7f555904671c0737819fe4d19bd6143de3f6c0 <80862cbf76c2646f709a57c4517aefe0b094c774

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.10; version=5a7f555904671c0737819fe4d19bd6143de3f6c0 <2f3eab368e313dba35fc2f51ede778bf7b030b54; version=5a7f555904671c0737819fe4d19bd6143de3f6c0 <39a2a6eb5c9b66ea7c8055026303b3aa681b49a5; version=5a7f555904671c0737819fe4d19bd6143de3f6c0 <805cea93e66ca7deaaf6ad3b67224ce47c104c2f; version=5a7f555904671c0737819fe4d19bd6143de3f6c0 <80862cbf76c2646f709a57c4517aefe0b094c774

Published CVSS scores

7.7CISA ADPCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1499Endpoint Denial of Service

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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