CVE-2021-30738

Arbitrary file overwrite via unsanitized hardlink paths

Published Sep 8, 2021 · Updated Aug 3, 2024

Path validation failure in Apple macOS Big Sur before 11.4 and Mojave before Security Update 2021-004 allows local users to overwrite arbitrary files. PackageKit inadequately sanitizes hardlink paths before using them, allowing a crafted hardlink to redirect a file write outside its intended destination. Execution of a malicious local application is required, and the consequence is limited to file integrity with no reported read, code-execution, or service-interruption impact.

CVSS severity5.5
Medium
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path validation failure in Apple macOS Big Sur before 11.4 and Mojave before Security Update 2021-004 allows local users to overwrite arbitrary files. PackageKit inadequately sanitizes hardlink paths before using them, allowing a crafted hardlink to redirect a file write outside its intended destination. Execution of a malicious local application is required, and the consequence is limited to file integrity with no reported read, code-execution, or service-interruption impact.

The record

CVE
CVE-2021-30738
Published
Sep 8, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
macOS
Classifications
T1565.001
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 <11.4
  2. Affected versionversion=unspecified <2021

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Apple · macOSversion=unspecified <11.4; version=unspecified <2021

Published CVSS scores

2.1NIST NVDAV:L/AC:L/Au:N/C:N/I:P/A:N
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/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 exploitUnconfirmed

Weakness, pattern, technique

T1565.001Stored Data Manipulation

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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