CVE-2026-84520: A buffer overflow was addressed with improved size validation

Q: How do I fix CVE-2026-84520?

macos: upgrade to 27.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-84520 being exploited?

CVE-2026-84520 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-84520 affect?

CVE-2026-84520 affects macos. Severity is critical (CVSS 9.8). A buffer overflow was addressed with improved size validation. This issue is fixed in macOS Golden Gate 27. A local attacker may be able to cause unexpected system termination or corrupt kernel memory.

Q: How urgent is CVE-2026-84520?

Priority 49/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-84520 is a critical-severity flaw (CVSS 9.8) affecting macos. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A buffer overflow was addressed with improved size validation. This issue is fixed in macOS Golden Gate 27. A local attacker may be able to cause unexpected system termination or corrupt kernel memory.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-120
Published	2026-09-14
Last modified	2026-09-16

Publisher (CNA): Apple Inc. · Vendor: apple

Last updated 2026-09-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-14 21:17 UTCPublished CVE record published
2026-09-16 17:14 UTCUpdated Record last modified

apple macos UPGRADE

Affected: < 27.0

Fixed in: 27.0

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-84520?

macos: upgrade to 27.0. Exact commands for each OS are on this page.

Is CVE-2026-84520 being exploited?

CVE-2026-84520 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-84520 affect?

CVE-2026-84520 affects macos. Severity is critical (CVSS 9.8). A buffer overflow was addressed with improved size validation. This issue is fixed in macOS Golden Gate 27. A local attacker may be able to cause unexpected system termination or corrupt kernel memory.

How urgent is CVE-2026-84520?

Priority 49/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

macOS vulnerabilities

Related CVEs

CVE-2026-86950 HIGH 8.8 EXPLOITED UPGRADE UPGRADE Apple Multiple Products Out-of-Bounds Write Vulnerability
CVE-2026-65339 MEDIUM 5.0 UPGRADE UPGRADE A logic issue was addressed with improved checks
CVE-2026-64767 CRITICAL 9.8 UPGRADE A buffer overflow was addressed with improved bounds checking
CVE-2026-28991 HIGH 7.5 UPGRADE UPGRADE An out-of-bounds read was addressed with improved bounds checking
CVE-2026-28864 LOW 3.3 UPGRADE UPGRADE This issue was addressed with improved permissions checking

References

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