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Vulnerabilities

Vulnerability · CVE-2021-30663

Apple Multiple Products WebKit Integer Overflow Vulnerability

Published May 3, 2021 · catalog updated Jun 16, 2026 · Apple Multiple Products

Patch now

CVE-2021-30663 is in the CISA known-exploited catalog, due Nov 17, 2021. Confirm Apple Multiple Products against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
High8.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
3.52%
Remediation
Remediation guidance
Affected products
cpe apple/ipados · cpe apple/iphone os · cpe apple/macos · cpe apple/safari · cpe apple/tvos · vendor Apple Multiple Products

Apple iOS, iPadOS, macOS, tvOS, and Safari WebKit contain an integer overflow vulnerability that leads to code execution when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe apple/ipadosversion unspecified
  • cpe apple/iphone osversion unspecified
  • cpe apple/macosversion unspecified
  • cpe apple/safariversion unspecified
  • cpe apple/tvosversion unspecified
  • vendor Apple Multiple Productsversion unspecified

How to fix CVE-2021-30663

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-30663 is in the CISA known-exploited catalog, due Nov 17, 2021. Confirm Apple Multiple Products against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Affected version ranges are not on this record. Apply updates per vendor instructions.

What should an analyst verify?

CWE-190: Integer Overflow; CWE-20: Improper Input Validation. EPSS 3.52%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 8, 2021 · Catalog

    Detected

    Apple iOS, iPadOS, macOS, tvOS, and Safari WebKit contain an integer overflow vulnerability that leads to code execution when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.

  2. Nov 3, 2021 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. Nov 17, 2021 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

    Apple iOS, iPadOS, macOS, tvOS, and Safari WebKit contain an integer overflow vulnerability that leads to code execution when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.

Sources

  • CISA KEVConfirmed exploitationCVE-2021-30663

    Apple iOS, iPadOS, macOS, tvOS, and Safari WebKit contain an integer overflow vulnerability that leads to code execution when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2021-30663

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-30663

    30-day exploitation probability 3.5%

    first.org
  • NIST NVDVulnerability recordCVE-2021-30663

    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.

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2021-30663

    Apple iOS, iPadOS, macOS, tvOS, and Safari WebKit contain an integer overflow vulnerability that leads to code execution when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and no

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.