CVE-2026-86871: An integer underflow was addressed with improved input validation

Q: How do I fix CVE-2026-86871?

macos: upgrade to 15.8, 26.7. Exact commands for each OS are on this page.

Q: Is CVE-2026-86871 being exploited?

CVE-2026-86871 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-2026-86871 affect?

CVE-2026-86871 affects macos. Severity is medium (CVSS 5.9). An integer underflow was addressed with improved input validation. This issue is fixed in macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7. An attacker with control of a network file server may be able to cause unexpected system t

Q: How urgent is CVE-2026-86871?

Priority 36/100. Remotely exploitable, no login, no user action

Routine

MEDIUM 5.9REMOTEUPGRADE

CVE-2026-86871 is a medium-severity flaw (CVSS 5.9) affecting macos. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An integer underflow was addressed with improved input validation. This issue is fixed in macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7. An attacker with control of a network file server may be able to cause unexpected system termination.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-20, CWE-190
Published	2026-10-20
Last modified	2026-11-03

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

Last updated 2026-11-03 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-20 01:17 UTCPublished CVE record published
2026-11-03 21:09 UTCUpdated Record last modified

apple macos UPGRADE

Affected: < 15.8 · >= 26.0 and < 26.7

Fixed in: 15.8, 26.7

Safe to downgrade to: a release before 26.0

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-2026-86871?

macos: upgrade to 15.8, 26.7. Exact commands for each OS are on this page.

Is CVE-2026-86871 being exploited?

CVE-2026-86871 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-2026-86871 affect?

CVE-2026-86871 affects macos. Severity is medium (CVSS 5.9). An integer underflow was addressed with improved input validation. This issue is fixed in macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7. An attacker with control of a network file server may be able to cause unexpected system t

How urgent is CVE-2026-86871?

Priority 36/100. Remotely exploitable, no login, no user action

Software pages

macOS vulnerabilities

Related CVEs

CVE-2026-112424 HIGH 7.1 UPGRADE An out-of-bounds read was addressed with improved bounds checking
CVE-2026-112425 LOW 3.3 UPGRADE UPGRADE An out-of-bounds read was addressed with improved bounds checking
CVE-2026-112428 MEDIUM 5.5 UPGRADE A logic issue was addressed with improved checks
CVE-2026-112429 MEDIUM 5.5 UPGRADE An out-of-bounds read was addressed with improved bounds checking
CVE-2026-112430 HIGH 7.8 UPGRADE An authentication issue was addressed with improved validation of user attributes

References

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