CVE-2021-1879

KEVApple iOS, iPadOS, and watchOS WebKit Cross-Site Scripting (XSS) Vulnerability

Description

Apple iOS, iPadOS, and watchOS WebKit contain an unspecified vulnerability that allows for universal cross-site scripting (XSS) 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.

This issue was addressed by improved management of object lifetimes. This issue is fixed in iOS 12.5.2, iOS 14.4.2 and iPadOS 14.4.2, watchOS 7.3.3. Processing maliciously crafted web content may lead to universal cross site scripting. 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:R/S:C/C:L/I:L/A:N

PublishedApr 2, 2021

Last modifiedJun 17, 2026

Added to KEVNov 3, 2021

Remediation dueNov 17, 2021

References

support.apple.com/en-us/HT212256Release NotesVendor Advisory
support.apple.com/en-us/HT212257Release NotesVendor Advisory
support.apple.com/en-us/HT212258Release NotesVendor Advisory
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1879US Government Resource

0 recent articles mention this CVE

Risk assessment · High

Actively exploited. Patch immediately.

Exploitation: Confirmed in the wild (CISA KEV)
Federal remediation deadline: Overdue by 1805 days
CVSS: 6.1 MEDIUM
EPSS (30-day exploit probability): 7.1% · top 6% of all CVEs
Weakness: CWE-79
Attack vector: Network, remotely reachable

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.