CVE-2021-1839

Local privilege escalation via Time Machine permissions

Published Sep 8, 2021 · Updated Aug 3, 2024

Improper privilege management in Time Machine in Apple macOS before Big Sur 11.3 allows local users to elevate privileges. Apple identifies incorrect permission logic in Time Machine but has not disclosed which operation or untrusted input triggers it. Exploitation requires local low-privileged access and results in privilege elevation on affected Big Sur, Catalina, and Mojave systems.

CVSS severity7.8
High
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper privilege management in Time Machine in Apple macOS before Big Sur 11.3 allows local users to elevate privileges. Apple identifies incorrect permission logic in Time Machine but has not disclosed which operation or untrusted input triggers it. Exploitation requires local low-privileged access and results in privilege elevation on affected Big Sur, Catalina, and Mojave systems.

The record

CVE
CVE-2021-1839
Published
Sep 8, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
macOS
Classifications
CWE-269, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 8, 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 <11.3
  2. Affected versionversion=unspecified <2021

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Apple · macOSversion=unspecified <11.3; version=unspecified <2021

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P

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

CWE-269Improper Privilege Management
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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