CVE-2021-1870

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

Description

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.

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..

CVSS 3.1 vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

PublishedApr 2, 2021

Last modifiedJun 17, 2026

Added to KEVNov 3, 2021

Remediation dueNov 17, 2021

References

lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JN6ZOD62CTO54CHTMJTHVEF6R2Y532TJ/Broken LinkMailing List
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L3L6ZZOU5JS7E3RFYGLP7UFLXCG7TNLU/Broken LinkMailing List
security.gentoo.org/glsa/202104-03Third Party Advisory
support.apple.com/en-us/HT212146Release NotesVendor Advisory
support.apple.com/en-us/HT212147Release NotesVendor Advisory
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1870US Government Resource

0 recent articles mention this CVE

Risk assessment · Critical

Actively exploited. Patch immediately.

Exploitation: Confirmed in the wild (CISA KEV)
Federal remediation deadline: Overdue by 1805 days
CVSS: 9.8 CRITICAL
EPSS (30-day exploit probability): 7.7% · top 5% of all CVEs
Weakness: NVD-CWE-noinfo
Attack vector: Network, remotely reachable
Preconditions: No privileges and no user interaction

Recommended actions

1.Apply updates per vendor instructions.
2.Treat as emergency change: patch or isolate internet-facing instances first.
3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.

Assessment is derived automatically from the live signals above; verify against your own asset inventory.