What is CVE-2021-30739?

CVE-2021-30739 is a high-severity vulnerability in Apple macOS, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2021-09-08.

How severe is CVE-2021-30739?

High severity. CVSS v3 base score is 7.8 out of 10.

Buffer overflow in Apple macOS

CVE-2021-30739

A local attacker may be able to elevate their privileges. This issue is fixed in macOS Big Sur 11.4, Security Update 2021-003 Catalina, Security Update 2021-004 Mojave. A memory corruption issue was addressed with improved validation.

Vulnerability class: Buffer Overflow

Published 2021-09-08 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.003 (23.0th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 23rd percentile — 23.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Apple macOS — versions unspecified
Apple Mac OS X — versions 10.14.6, 10.15.7

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

support.apple.com/en-us/HT212529 (Vendor Advisory)
support.apple.com/en-us/HT212530 (Vendor Advisory)
support.apple.com/en-us/HT212531 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-30739?: CVE-2021-30739 is a high-severity vulnerability in Apple macOS, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2021-09-08.
How severe is CVE-2021-30739?: High severity. CVSS v3 base score is 7.8 out of 10.