What is CVE-2026-64691?

CVE-2026-64691 is a critical-severity vulnerability in Apple macOS, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 9.8/10. Published 2026-07-27.

How severe is CVE-2026-64691?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Apple macOS

CVE-2026-64691

A buffer overflow was addressed with improved size validation. This issue is fixed in macOS Tahoe 26.6. An app may be able to cause unexpected system termination.

Vulnerability class: Buffer Overflow

EPSS: 0.004 (37.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Apple Macos — versions 0

Weakness classification (CWE)

CWE-120 — Buffer Copy without Checking Size of Input (Classic Buffer Overflow)

References

product-security@apple.com (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2026-64691?: CVE-2026-64691 is a critical-severity vulnerability in Apple macOS, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 9.8/10. Published 2026-07-27.
How severe is CVE-2026-64691?: Critical severity. CVSS v3 base score is 9.8 out of 10.