What’s Vulnerable › Vulnerabilities

CVE-2020-9991

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-12-08 · updated 2026-06-17

Description

This issue was addressed with improved checks. This issue is fixed in macOS Big Sur 11.0.1, watchOS 7.0, iOS 14.0 and iPadOS 14.0, iCloud for Windows 7.21, tvOS 14.0. A remote attacker may be able to cause a denial of service.

Affected products

• Apple iCloud for Windows: before 7.21; from 11.0 before 11.4 — fixed in 11.4, 7.21
• Apple iPadOS: before 14.0 — fixed in 14.0
• Apple Iphone Os: before 14.0 — fixed in 14.0
• macOS: before 11.0.1 — fixed in 11.0.1
• Apple tvOS: before 14.0 — fixed in 14.0
• Apple watchOS: before 7.0 — fixed in 7.0

How to fix

Upgrade to a fixed version: Apple iCloud for Windows 11.4, 7.21; Apple iPadOS 14.0; Apple Iphone Os 14.0; macOS 11.0.1; Apple tvOS 14.0; Apple watchOS 7.0. Check the vendor advisory for mitigations.

References

• http://seclists.org/fulldisclosure/2020/Dec/32
• https://lists.apache.org/thread.html/rf9fa47ab66495c78bb4120b0754dd9531ca2ff0430f6685ac9b07772%40%3Cdev.mina.apache.org%3E
• https://support.apple.com/en-us/HT211843
• https://support.apple.com/en-us/HT211844
• https://support.apple.com/en-us/HT211847
• https://support.apple.com/en-us/HT211850
• https://support.apple.com/en-us/HT211931
• https://support.apple.com/kb/HT211846
• http://seclists.org/fulldisclosure/2020/Dec/32
• https://lists.apache.org/thread.html/rf9fa47ab66495c78bb4120b0754dd9531ca2ff0430f6685ac9b07772%40%3Cdev.mina.apache.org%3E
• https://support.apple.com/en-us/HT211843
• https://support.apple.com/en-us/HT211844

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