CVE-2021-1821

Name: CVE-2021-1821
Creator: NVD / NIST
Published: 2021-10-28T19:15:08.667+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 0.64%

Last modified Jun 17, 2026

CVE-2021-1821 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. A logic issue was addressed with improved state management. This issue is fixed in watchOS 7.6, macOS Big Sur 11.5. EPSS estimates a 0.64% chance of exploitation in the next 30 days.

Description

A logic issue was addressed with improved state management. This issue is fixed in watchOS 7.6, macOS Big Sur 11.5. Visiting a maliciously crafted webpage may lead to a system denial of service.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

EPSS Probability

0.64%

45.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Apple	Macos	< 11.5
Apple	Watchos	< 7.6

References

https://support.apple.com/en-us/HT212602Vendor Advisory
https://support.apple.com/en-us/HT212605Vendor Advisory
https://support.apple.com/en-us/HT212602Vendor Advisory
https://support.apple.com/en-us/HT212605Vendor Advisory

Timeline

Published: Oct 28, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-1821?

A logic issue was addressed with improved state management. This issue is fixed in watchOS 7.6, macOS Big Sur 11.5. Visiting a maliciously crafted webpage may lead to a system denial of service.

How severe is CVE-2021-1821?

CVE-2021-1821 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.64% probability of exploitation in the next 30 days.

How do I fix CVE-2021-1821?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-1821?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST