High severity · published Sep 8, 2021
CVE-2021-30663
Apple Multiple Products WebKit Integer Overflow Vulnerability
In wildKEV
8.8
CVSS
3.5%
EPSS
Yes
On KEV
Description
An integer overflow was addressed with improved input validation. This issue is fixed in iOS 14.5.1 and iPadOS 14.5.1, tvOS 14.6, iOS 12.5.3, Safari 14.1.1, macOS Big Sur 11.3.1. Processing maliciously crafted web content may lead to arbitrary code execution.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)3.5% · higher than 89% of CVEs
Exploited in the wildYes
CISA KEVListed Nov 3, 2021
Federal remediation dueNov 17, 2021
Ransomware campaign useNot known
Affected products
Which versions
MA
macOS · Apple
before 11.3; before 14.5; before 12.5; before 14.6; before 14.1 · source: vendor, NVD
IO
iOS · Apple
14.0 before 14.5.1 · source: NVD
SA
Safari · Apple
before 14.1.1 · source: NVD
TV
Tvos · Apple
before 14.6 · source: NVD
MP
Multiple Products · Apple
All versions, or not specified · source: KEV
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-30663
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-30663
CISA KEV catalogue
https://www.cisa.gov/known-exploited-vulnerabilities-catalog
x_refsource_MISC
https://support.apple.com/en-us/HT212532
x_refsource_MISC
https://support.apple.com/en-us/HT212534
x_refsource_MISC
https://support.apple.com/en-us/HT212341
x_refsource_MISC
https://support.apple.com/en-us/HT212335
x_refsource_MISC
https://support.apple.com/en-us/HT212336
More from macOS
10.0
CVE-2025-43300
Apple iOS, iPadOS, and macOS Out-of-Bounds Write Vulnerability
10.0
CVE-2025-24201
Apple Multiple Products WebKit Out-of-Bounds Write Vulnerability
10.0
CVE-2025-24085
Apple Multiple Products Use-After-Free Vulnerability
9.8
CVE-2026-65400
Apple macOS Improper Authentication Vulnerability
9.8
CVE-2025-31200
Apple Multiple Products Memory Corruption Vulnerability