What’s Vulnerable › Vulnerabilities

CVE-2021-1821

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-10-28 · updated 2026-06-17

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.

Affected products

• Apple macOS: before 11.5 — fixed in 11.5
• Apple watchOS: before 7.6 — fixed in 7.6

How to fix

Upgrade to a fixed version: Apple macOS 11.5; Apple watchOS 7.6. Check the vendor advisory for mitigations.

References

• https://support.apple.com/en-us/HT212602
• https://support.apple.com/en-us/HT212605
• https://support.apple.com/en-us/HT212602
• https://support.apple.com/en-us/HT212605

Get alerted when CVE-2021-1821 or the next vulnerability affects your stack