Vulnerability

CVE-2021-1879

Medium· 6.1KEVCVSS6.1EPSS1%

.rules3/5

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.

Threat signal

71/100

High

Severity

medium

CVSS

6.1

EPSS

Active

KEV

CISA KEV — actively exploited

1669d overdue

AffectedApple — iOS, iPadOS, and watchOS

Added to KEV

2021-11-03

Federal patch due (BOD 22-01)

2021-11-17

Required action (CISA verbatim)

Apply updates per vendor instructions.

Vendor advisory + references

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

CISA 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.”

CVSS

v3.1Open in FIRST calculator →

6.1/ 10MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredNoneUnauthenticated — no credentials needed.
User InteractionRequiredRequires user action (click, file open, etc).
ScopeChangedImpact extends beyond the vulnerable component (e.g. sandbox escape).
Confidentiality ImpactLowSome data disclosure; attacker doesn't fully control what.
Integrity ImpactLowSome data modification; attacker doesn't fully control extent.
Availability ImpactNoneNo availability impact.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

0.81%

probability of exploitation in next 30 days

p75

higher than 75% of all CVEs

3-day trend↑ 0pp

Low exploitation likelihood — defer if no other signals fire.

Vendor VEX

No VEX statements published for CVE-2021-1879. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCAttend

Active exploitation with limited impact — coordinate patching

exploitation: active
automatable: no
impact: partial
mission: support

Lifecycle

2021-11-03Added to CISA KEVransomware: Unknown
2021-11-03Published
2021-11-17Federal patch due (BOD 22-01)
2026-06-12Last modified1 source

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.