Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability

Are you affected?

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

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• cpe apple/ipadosversion unspecified
• cpe apple/iphone osversion unspecified
• cpe apple/mac os x10.15.7
• cpe apple/macosversion unspecified
• cpe debian/debian linux10.0
• cpe fedoraproject/fedora33
• vendor Apple iOS, iPadOS, and macOSversion unspecified

How to fix CVE-2021-1871

• Recommended remediation

  Apply updates per vendor instructions. CISA due date Nov 17, 2021.

• Official advisories

  • CISA KEV · cisa.gov
  • CVE.org · cve.org
  • FIRST EPSS · first.org
  • NIST NVD · nvd.nist.gov
  • VulnCheck KEV · vulncheck.com

What to do

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

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. Apr 2, 2021 · Catalog

   Detected

   A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

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

   A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

Sources

• CISA KEVConfirmed exploitationCVE-2021-1871

  Apple iOS, iPadOS, and macOS WebKit contain an unspecified logic vulnerability that allows a remote attacker to execute code. 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-2021-1871

  Official CVE identifier

  cve.org
• FIRST EPSSExploitation probabilityCVE-2021-1871

  30-day exploitation probability 7.0%

  first.org
• NIST NVDVulnerability recordCVE-2021-1871

  A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a re

  nvd.nist.gov
• VulnCheck KEVConfirmed exploitationCVE-2021-1871

  Apple iOS, iPadOS, and macOS WebKit contain an unspecified logic vulnerability that allows a remote attacker to execute code. 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 HT

  vulncheck.com

References

• VulnCheck exploitation evidence · docs.google.com
• Broken Link · lists.fedoraproject.org
• CISA note · nvd.nist.gov
• Release Notes · support.apple.com
• Release Notes · support.apple.com
• VulnCheck exploitation evidence · cisa.gov
• Mailing List · debian.org

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.