Is CVE-2021-1879 in the CISA KEV catalog?

Yes. CVE-2021-1879 is on the CISA Known Exploited Vulnerabilities list, added 2021-11-03.

What is the CVSS severity of CVE-2021-1879?

CVE-2021-1879 has a CVSS v3 base score of 6.1 (MEDIUM).

What is the EPSS score for CVE-2021-1879?

CVE-2021-1879 has an EPSS score of 7.08% (93th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2021-1879

MEDIUMCISA KEVEPSS 93th pctl

6.1

CVSS v3

NVD

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..

CWE-79Cross-Site Scripting (XSS)

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeChanged

Impact

ConfidentialityLow

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

7.08%probability of exploitation in 30 days

93rdpercentile

High risk: more likely to be exploited than 93% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

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

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.

Apply updates per vendor instructions.

Remediation due: 2021-11-17

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-10-23.