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Full vulnerability report · 2021
CVE-2021-30663High confidence

Apple Multiple Products WebKit Integer Overflow Vulnerability

Apple · Multiple Products

8.8HighCVSS 3.1
Recommended action
Protect now

CISA confirms exploitation in the wild and lists 2021-11-17 as the remediation due date.

Fix not verified
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 3 Nov 2021

Evidence used

  • CISA confirms exploitation in the wild.
  • EPSS is 3.52% for the current model date.

Compensating controls

  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Apple Multiple Products and falls inside the recorded affected range.
  2. Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

9 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcewebkit2gtkVendor fix publishedDebian records a fixed source-package version for this release.2.32.3-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian trixietrixie · sourcewpewebkitVendor fix publishedDebian records a fixed source-package version for this release.2.32.3-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcewebkit2gtkVendor fix publishedDebian records a fixed source-package version for this release.2.32.3-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcewpewebkitVendor fix publishedDebian records a fixed source-package version for this release.2.32.3-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcewebkit2gtkVendor fix publishedDebian records a fixed source-package version for this release.2.32.3-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcewpewebkitVendor fix publishedDebian records a fixed source-package version for this release.2.32.3-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcewebkit2gtkVendor fix publishedDebian records a fixed source-package version for this release.2.32.3-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcewpewebkitVendor fix publishedDebian records a fixed source-package version for this release.2.32.3-1Debian Security Tracker ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archiveqtwebkit-opensource-srcUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2021-17580

CISA KEV mirrored by ENISA

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.

EUVD state
Present in the current official mapping
Known exploitation
Recorded by ENISA since 3 Nov 2021. Evidence sources: cisa_kev.
ENISA score
7.8 · CVSS 3.1
Advisory evidence
7 linked advisory records
Explicit mitigation evidence

Only statements that explicitly mention a fix, patch, update, workaround or mitigation are shown here.

  • csaf_suse · SUSE-SU-2021:2598-1Security update for webkit2gtk3
  • csaf_opensuse · openSUSE-SU-2021:2598-1Security update for webkit2gtk3
  • csaf_opensuse · openSUSE-SU-2021:1101-1Security update for webkit2gtk3
  • csaf_suse · SUSE-SU-2021:2762-1Security update for webkit2gtk3
  • csaf_suse · SUSE-SU-2021:2600-1Security update for webkit2gtk3
  • csaf_redhat · RHSA-2021:4381Red Hat Security Advisory: GNOME security, bug fix, and enhancement update
  • csaf_redhat · RHSA-2025:10364Red Hat Security Advisory: webkitgtk4 security update
Recommended actionProtect now

CISA confirms exploitation in the wild and lists 2021-11-17 as the remediation due date.

Fix not verified
01

What, why and how

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.

What

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.

Why

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

How

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

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.

Why

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

How

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2021-11-03.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Integer Overflow or Wraparound → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
Required interaction required
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-190 ↗

CWE-190: Integer Overflow or Wraparound. The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-190CISA KEV
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2021-17580Known-exploited evidence recorded

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.

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20210915Security Bulletin 15 Sep 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 15 Sep 2021, published on 15 September 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-398Multiples vulnérabilités dans les produits Apple

ecord?id=CVE-2020-36226 Référence CVE CVE-2020-36227 https://www.cve.org/CVERecord?id=CVE-2020-36227 Référence CVE CVE-2020-36228 https://www.cve.org/CVERecord?id=CVE-2020-36228 Référence CVE CVE-2020-36229 https://www.cve.org/CVERecord?id=CVE-2020-36229 Référence CVE CVE-2020-36230 https://www.cve.org/CVERecord?id=CVE-2020-36230 Référence CVE CVE-2021-1883 https://www.cve.org/CVERecord?id=CVE-2021-1883 Référence CVE CVE-2021-1884 https://www.cve.org/CVERecord?id=CVE-2021-1884 Référence CVE CVE-2021-21779 https://www.cve.org/CVERecord?id=CVE-2021-21779 Référence CVE CVE-2021-23841 https://www.cve.org/CVERecord?id=CVE-2021-23841 Référence CVE CVE-2021-30663 https://www.cve.org/CVERecord?id=CVE-2021-30663 Référence CVE CVE-2021-30665 https://www.cve.org/CVERecord?id=CVE-2021-30665 Référence CVE CVE-2021-30667 https://www.cve.org/CVERecord?id=CVE-2021-30667 Référence CVE CVE-2021-30668 https://www.cve.org/CVERecord?id=CVE-2021-30668 Référence CVE CVE-2021-30669 https://www.cve.org/CVERecord?id=CVE-2021-30669 Référence CVE CVE-2021-30671 https://www.cve.org/CVERecord?id=CVE-2021-30671 Référence CVE CVE-2021-30673 https://www.cve.org/CVERecord?id=CVE-2021-30673 Référence CVE CVE-2021-30674 https://www.cve.org/CVERecord?id=CVE-2021-30674 Référence CVE CVE-2021-30676 https://www.cve.org/CVERecord?id=

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-345Multiples vulnérabilités dans Apple Safari

De multiples vulnérabilités ont été découvertes dans Apple Safari. Elles permettent à un attaquant de provoquer une exécution de code arbitraire à distance.

Official advisory ↗
CERT-FR · French · CERTFR-2021-AVI-336Multiples vulnérabilités dans les produits Apple

De multiples vulnérabilités ont été découvertes dans les produits Apple. Elles permettent à un attaquant de provoquer une exécution de code arbitraire à distance.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-013500複数の Apple 製品における整数オーバーフローの脆弱性

複数の Apple 製品には、整数オーバーフローの脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix not verified
Affected
macOS: unspecified < 11.3, unspecified < 14.5, unspecified < 12.5, unspecified < 14.6, unspecified < 14.1
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 8 Sept 2021 · Last source change 21 Oct 2025, 23:25 UTC · CWE-190 · Integer Overflow or Wraparound

CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2021-17580
Product sourceCISA KEV
Remediation sourceCVE/CNA references
CWE sourceCISA ADP
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    unspecified < 11.3; unspecified < 14.5; unspecified < 12.5; unspecified < 14.6; unspecified < 14.1 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    macOS: unspecified < 11.3, unspecified < 14.5, unspecified < 12.5, unspecified < 14.6, unspecified < 14.1 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
ENISA EUVD · EUVD-2021-17580↗CISA KEV record↗CVE authority or vendor reference↗Vendor advisory↗Vendor advisory↗Vendor advisory↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2021-30663 · cve.blacktree.nl