CVE-2021-30665: Apple Multiple Products WebKit Memory Corruption Vulnerability

Reference page built from the source records below, each shown as its source publishes it. Dataset version ref-a4352d8e5ba2, updated 2026-11-02T23:39:54.475Z.

CISA Known Exploited Vulnerabilities

Name: Apple Multiple Products WebKit Memory Corruption Vulnerability
Vendor: Apple
Product: Multiple Products
Added to the catalog: 2021-11-03
Due date for US federal agencies: 2021-11-17
Weaknesses: CWE-787
Catalog version: 2026.10.30

Apple iOS, iPadOS, macOS, watchOS, and tvOS WebKit contain a memory corruption 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.

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-2021-30665

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: 2021-09-08T15:15:13.507
Last modified: 2026-06-17T03:50:39.197
Weaknesses: CWE-787

A memory corruption issue was addressed with improved state management. This issue is fixed in watchOS 7.4.1, iOS 14.5.1 and iPadOS 14.5.1, tvOS 14.6, iOS 12.5.3, macOS Big Sur 11.3.1. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

Metric	Score	Severity	Vector	Scored by
CVSS 3.1	8.8	HIGH	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H	[email protected] (Primary)
CVSS 3.1	8.8	HIGH	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H	134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary)
CVSS 2.0	6.8	MEDIUM	AV:N/AC:M/Au:N/C:P/I:P/A:P	[email protected] (Primary)

References

https://support.apple.com/en-us/HT212335 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212336 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212339 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212341 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212532 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212335 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212336 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212339 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212341 (Release Notes, Vendor Advisory)
https://support.apple.com/en-us/HT212532 (Release Notes, Vendor Advisory)
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30665 (Third Party Advisory, US Government Resource)

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

Read on 2026-11-02T23:41:59.479Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-30665

CVE record

Assigner: apple
State: PUBLISHED
Published: 2021-09-08T14:25:00.000Z
Updated: 2025-10-21T23:25:34.957Z
Problem types: Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited.

References

Read on 2026-11-03T01:07:32.909Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/30xxx/CVE-2021-30665.json

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

CWE-787: Out-of-bounds Write

Harden: Variable Initialization (acts on Subroutine)
Harden: Trusted Library (acts on Subroutine)
Harden: Software Update (acts on Software)
Model: Asset Vulnerability Enumeration (acts on Software)
Model: Software Inventory (acts on Software)
Harden: Domain Logic Validation (acts on Subroutine)
Harden: Credential Scrubbing (acts on Subroutine)
Isolate: Application-based Process Isolation (acts on Subroutine)
Restore: Restore Software (acts on Software)

D3FEND ontology version 1.6.0.

Read on 2026-11-03T00:02:57.820Z under licence d3fend-terms-of-use@f98cbc7e from https://d3fend.mitre.org/api/weakness/cwe/CWE-787.json

MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/

Sources and licences

CISA
Source: CISA Catalog of Known Exploited Vulnerabilities, version 2026.10.30, CC0 1.0. Use of this data does not imply endorsement by CISA or DHS.
CC0 1.0 Universal
National Vulnerability Database (NIST)
This product uses the NVD API but is not endorsed or certified by the NVD.
NVD API Terms of Use (NIST publications in the public domain, 17 U.S.C. 105)
CVE Program, The MITRE Corporation
Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation. CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy.
CVE Program Terms of Use ("CVE Usage" licence)
MITRE D3FEND
MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/
MITRE D3FEND Terms of Use (site + knowledge graph); source repo MIT

Cite this page

Dragons Eye Ransomware Tracker, "CVE-2021-30665: Apple Multiple Products WebKit Memory Corruption Vulnerability",
entity page, dataset version ref-a4352d8e5ba2, updated 2026-11-02T23:39:54.475Z,
https://ransomware-tracker.com/cve/CVE-2021-30665 (accessed 2026-11-03).
Underlying source: CISA Catalog of Known Exploited Vulnerabilities, version 2026.10.30.
Underlying source: National Vulnerability Database (NIST), CVE API 2.0, record last modified 2026-06-17T03:50:39.197.
Underlying source: CVE List (CVE Program, The MITRE Corporation), record updated 2025-10-21T23:25:34.957Z.
Underlying source: MITRE D3FEND, ontology version 1.6.0.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.

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