How severe is CVE-2021-1879?

CVE-2021-1879 has a CVSS 3.1 base score of 6.1 (MEDIUM). EPSS estimates a 7.1% probability of exploitation in the next 30 days. It is listed in the CISA Known Exploited Vulnerabilities catalog.

CVE-2021-1879: Apple iOS, iPadOS, and watchOS WebKit Cross-Site

CISA Known Exploited Vulnerabilities

Apple iOS, iPadOS, and watchOS WebKit Cross-Site Scripting (XSS) Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.

Added to KEV

2021-11-03

Remediation due

2021-11-17

Required action
Apply updates per vendor instructions.

CISA notes
https://nvd.nist.gov/vuln/detail/CVE-2021-1879

Description

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..

Severity

CVSS 3.1 · CISA6.1 MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

SSVC · CISA-ADP

Exploitationactive

Automatableno

Technical impactpartial

Exploitation Context

as of October 14, 2026

All KEV statistics→

CISA added CVE-2021-1879 to the KEV catalog 215 days after its CVE record was published.
It is one of 95 Apple entries in the CISA KEV catalog, and one of 23 added in 2021.
Its current EPSS score (7.1%) is higher than that of 22% of CISA KEV entries.

Affected Products

Vendor	Product	Affected versions
Apple	Apple iOS and iPadOS	unspecified to <14.4
Apple	Apple iOS	unspecified to <12.5
Apple	Apple watchOS	unspecified to <7.3

References

3 Links

Other references

Record Details

Published

2021-04-02

Last updated

2025-10-21

Assigner (CNA)

apple

Credited to

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CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.