CVE-2021-1821 Denial of service in macOS

What is CVE-2021-1821?

CVE-2021-1821 is a medium-severity denial of service vulnerability in Apple Macos, published on 28 Oct 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official 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.

Which versions are affected by CVE-2021-1821?

It affects 2 products.

Products include Apple Macos, Apple Watchos.

How do I fix CVE-2021-1821?

No fix has been published for CVE-2021-1821 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-1821 being exploited?

There is no known exploitation of CVE-2021-1821 in the wild and no public exploit code.

Other vulnerabilities in Apple Macos

• CVE-2026-65400 Apple macOS Improper Authentication Exploited Critical 9.8
• CVE-2024-44146 Security feature bypass in macOS Critical 10.0
• CVE-2024-44148 Security feature bypass in macOS Critical 10.0
• CVE-2023-38586 Security feature bypass in macOS Critical 10.0
• CVE-2023-40455 Security feature bypass in macOS Critical 10.0

All Apple Macos vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-p9hx-m56p-r6wc.