Secuno
ENNL
Book demo

CVE-2021-1879

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

6.1 MEDIUMActively exploited (CISA KEV)EPSS 7.08%
  1. Published2 Apr 2021
  2. Added to CISA KEV3 Nov 2021
  3. Remediation due17 Nov 2021
Actively exploited (CISA KEV)

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.

Added to KEV: 3 Nov 2021Federal remediation due: 17 Nov 2021

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..

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected products

Apple iPadOS< 14.4.2
Apple iPhone OS≥ 13.0 < 14.4.2 · < 12.5.2
Apple Watchos< 7.3.3

Remediation

Fixed in
Apple iPadOS≥ 14.4.2
Apple iPhone OS≥ 14.4.2
Apple Watchos≥ 7.3.3

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

CVE-2026-1095588.7
EdgeEver 1.6.0 through 1.112.0 contains a stored cross-site scripting vulnerability in…
CVE-2026-1095578.7
EdgeEver through 1.112.0 contains a stored cross-site scripting vulnerability in…
CVE-2026-1054108.7
A Stored Cross-site Scripting (XSS) vulnerability affecting Tuleap Enterprise Edition…
CVE-2026-1054098.7
A Stored Cross-site Scripting (XSS) vulnerability affecting Tuleap Enterprise Edition…
CVE-2026-1054088.7
A Stored Cross-site Scripting (XSS) vulnerability affecting Tuleap Enterprise Edition…
CVE-2026-962278.8
The Piotnet Forms WordPress plugin through 1.0.30 does not authenticate or validate a…

Frequently asked

Is CVE-2021-1879 being actively exploited?

Yes. CVE-2021-1879 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 3 Nov 2021.

How severe is CVE-2021-1879?

CVE-2021-1879 has a CVSS 3.1 base score of 6.1, rated medium. EPSS estimates a 7.08% probability of exploitation.

Which products are affected by CVE-2021-1879?

Affected products include Apple iPadOS, Apple iPhone OS, Apple Watchos.

How do I fix CVE-2021-1879?

Upgrade affected software to a fixed version, for example Apple iPadOS 14.4.2, Apple iPhone OS 14.4.2, Apple Watchos 7.3.3 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-1879 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

See how prioritisation worksBook a demo

Get Patch this first every Monday

Five vulnerabilities that matter this week, ranked on real exploitation. Plain language, one email, no spam.

You can unsubscribe with one click from every issue. We handle your details as described in our privacy policy.

Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.