CVE-2021-30857

Kernel code execution via improper locking

Published Aug 24, 2021 · Updated Aug 3, 2024

Race condition in the macOS kernel allows local users to execute arbitrary code with kernel privileges on vulnerable Big Sur and Catalina systems. Apple identifies the kernel as the locus and says improved locking closes the race, but it has not published the shared resource or code path that was improperly synchronized. Execution of a malicious application is required, after which attacker-controlled code runs with kernel privileges and can compromise the operating system.

CVSS severity7.8
High
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in the macOS kernel allows local users to execute arbitrary code with kernel privileges on vulnerable Big Sur and Catalina systems. Apple identifies the kernel as the locus and says improved locking closes the race, but it has not published the shared resource or code path that was improperly synchronized. Execution of a malicious application is required, after which attacker-controlled code runs with kernel privileges and can compromise the operating system.

The record

CVE
CVE-2021-30857
Published
Aug 24, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
macOS
Classifications
CWE-362, CAPEC-26, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 24, 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?

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

  1. Affected versionversion=unspecified <11.6
  2. Affected versionversion=unspecified <14.8
  3. Affected versionversion=unspecified <15
  4. Affected versionversion=unspecified <2021
  5. Affected versionversion=unspecified <8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Apple · macOSversion=unspecified <11.6; version=unspecified <14.8; version=unspecified <15; version=unspecified <2021; version=unspecified <8

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
7.6NIST NVDAV:N/AC:H/Au:N/C:C/I:C/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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CAPEC-26Leveraging Race Conditions
T1068Exploitation for Privilege Escalation

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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