CVE-2021-1871: Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability

CISA Known Exploited Vulnerabilities

Name

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

Vendor

Apple

Product

iOS, iPadOS, and macOS

Added to the catalog

2021-11-03

Due date for US federal agencies

2021-11-17

Weaknesses

CWE-1173

Catalog version

2026.10.30

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.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• https://nvd.nist.gov/vuln/detail/CVE-2021-1871

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2021-04-02T19:15:20.663

Last modified

2026-06-17T03:32:41.847

Weaknesses

NVD-CWE-noinfo

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..

References

• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/ (Broken Link, Mailing List)
• https://support.apple.com/en-us/HT212146 (Release Notes, Vendor Advisory)
• https://support.apple.com/en-us/HT212147 (Release Notes, Vendor Advisory)
• https://www.debian.org/security/2021/dsa-4923 (Mailing List, Third Party Advisory)
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/ (Broken Link, Mailing List)
• https://support.apple.com/en-us/HT212146 (Release Notes, Vendor Advisory)
• https://support.apple.com/en-us/HT212147 (Release Notes, Vendor Advisory)
• https://www.debian.org/security/2021/dsa-4923 (Mailing List, Third Party Advisory)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1871 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:51.476Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-1871

CVE record

Assigner

apple

State

PUBLISHED

Published

2021-04-02T18:06:58.000Z

Updated

2025-10-21T23:25:49.836Z

Problem types

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.

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..

References

• https://support.apple.com/en-us/HT212147
• https://support.apple.com/en-us/HT212146
• FEDORA-2021-864dc37032
• DSA-4923

Read on 2026-11-03T01:05:37.307Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/1xxx/CVE-2021-1871.json