CASCACascade Atlas

Evidence dossier

CVE-2021-1879

CVE-2021-1879

56.1–75.6Priority evidence range
As known Jul 19, 2026, 5:00 AM UTCgen-56ccdaf9

Normalized restatement

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..

State
PUBLISHED
Published
Apr 2, 2021
Updated
Oct 21, 2025
Evidence coverage
72%
CISA KEVCatalog member

Apply updates per vendor instructions.

FIRST EPSS7.08%

2026-07-18 · v2026.06.15 · percentile 93.5%

Source stateConflict visible

Distinct CVSS assessments remain side by side; none are averaged.

Source comparison

Who said what

appleoriginal assertion
container

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..

CISA-ADPindependent enrichment
container

CISA ADP Vulnrichment

CVEderivative copy
container

CVE Program Container

CISA KEVoriginal assertion
observed_exploitation

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

FIRST EPSSoriginal assertion
model_probability

Probability 0.070820000000; percentile 0.935060000000

Applicability

Cited product scope

Trace impact →
AppleiOS
[{"status": "affected", "version": "unspecified", "lessThan": "12.5", "versionType": "custom"}]unknown
AppleiOS and iPadOS
[{"status": "affected", "version": "unspecified", "lessThan": "14.4", "versionType": "custom"}]unknown
ApplewatchOS
[{"status": "affected", "version": "unspecified", "lessThan": "7.3", "versionType": "custom"}]unknown
Unknown vendorUnknown product
cpe:2.3:o:apple:ipados:*:*:*:*:*:*:*:*; end excluding 14.4.2supported
Unknown vendorUnknown product
cpe:2.3:o:apple:iphone_os:*:*:*:*:*:*:*:*; end excluding 12.5.2supported
Unknown vendorUnknown product
cpe:2.3:o:apple:iphone_os:*:*:*:*:*:*:*:*; start including 13.0; end excluding 14.4.2supported
Unknown vendorUnknown product
cpe:2.3:o:apple:watchos:*:*:*:*:*:*:*:*; end excluding 7.3.3supported

Assessments

CVSS by origin

6.1
nvd@nist.govCVSS 3.1 · role PrimaryCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3
nvd@nist.govCVSS 2.0 · role PrimaryAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1
134c704f-9b21-4f2e-91b3-4a467353bcc0CVSS 3.1 · role SecondaryCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1
CISA-ADPCVSS 3.1 · role unknownCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Limitations and unknowns

  • KEV membership is authoritative for the catalog, not proof of exposure in any environment.
  • EPSS is a dated model probability and not an individual-environment prediction.
  • Affected or fixed status applies only to the exact cited product and version scope; unresolved scope remains unknown.
  • NVD-carried upstream facts remain derivative and are not independent corroboration.
  • Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
  • NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
  • Factor D is unknown in Public Core because no accepted canonical mapping-obligation ledger is present.
  • Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.