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CVE-2021-1870

CRITICAL
9.8
CVSS Score
Published: April 2, 2021 at 06:06 PM UTC
Updated: June 17, 2026 at 03:32 AM UTC
5 products affected across 3 vendorsmacOSFedoraiPhone OS

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Severity
CRITICAL9.8
Exploitation
CISA KEV
Exploit prediction
EPSS 8%
SSVC
Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score7.7%

EPSS (Exploit Prediction Scoring System) estimates a 7.7% chance this CVE is exploited in the wild within the next 30 days — higher than 95% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

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
Apply updates per vendor instructions.
Ransomware Use
Unknown
Added to KEV
Nov 3, 2021
Remediation Due
Nov 17, 2021
1807 days overdue
Notes
https://nvd.nist.gov/vuln/detail/CVE-2021-1870

Description

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..

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

iPadOS· Apple
95%
v < 14.4
Affected range stops below 14.4, so it looks safe — our inference, not a vendor statement
iPhone OS· Apple
95%
v < 14.4
Affected range stops below 14.4, so it looks safe — our inference, not a vendor statement
macOS· Apple
95%
v < 11.210.15 ≤ v < 10.15.711.0.1 ≤ v < 11.210.15.710.15.7 security_update_2020-110.15.7 supplemental_update
Affected range stops below 10.15.7, so it looks safe — our inference, not a vendor statement
Affected range stops below 11.2, so it looks safe — our inference, not a vendor statement
Fedora· Fedora Projectrpm
95%
3233
WebKitGTK· Webkitgtk
95%
v < 2.30.6
Affected range stops below 2.30.6, so it looks safe — our inference, not a vendor statement

References (6)

Vendor Advisoryx_refsource_FEDORABroken LinkMailing List
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN6ZOD62CTO54CHTMJTHVEF6R2Y532TJ/
Vendor Advisoryx_refsource_FEDORABroken LinkMailing List
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/
Vendor Advisoryx_refsource_GENTOOThird Party Advisory
Source: [email protected]
https://security.gentoo.org/glsa/202104-03
x_refsource_MISCRelease NotesVendor Advisory
Source: [email protected]
https://support.apple.com/en-us/HT212146
x_refsource_MISCRelease NotesVendor Advisory
Source: [email protected]
https://support.apple.com/en-us/HT212147
US Government Resource
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1870

SSVC — Action Prioritization

SSVCActiveAutomatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

9.8CRITICALCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
NVD-CWE-noinfo

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