Threats / Apple / CVE-2021-1879
CVE-2021-1879
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Apple iOS, iPadOS, and watchOS vulnerability
WebKit in Apple iOS, iPadOS, and watchOS contains a cross-site scripting vulnerability allowing attackers to execute arbitrary scripts through maliciously crafted web content.
Verdict
Today item — known-exploited.
A universal XSS flaw in WebKit enables attackers to inject and execute malicious scripts in the context of trusted web applications, potentially compromising user data and device security across multiple Apple platforms.
CISA KEV Yes · 2021-11-034EPSS 0.07082 (verify live)5CVSS 6.1 (CISA)3CISA SSVC Exploitation: active · Automatable: no · Impact: partial3
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
10 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
Probability (EPSS)
EPSS 0.07082 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N) · Affected: Apple, iOS, iPadOS, and watchOS. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-79 Cross-site Scripting (XSS) — weakness family: Web / client.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 215 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft malicious web content designed to exploit the WebKit HTML parser vulnerability.
Business
User devices running iOS, iPadOS, or watchOS become vectors for script injection attacks affecting confidentiality and integrity of web-based interactions.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I deliver the malicious content through web pages, emails, or compromised websites that users visit in Safari or other WebKit-based browsers.
Business
Attack surface expands across all Apple platforms and third-party applications relying on WebKit, multiplying exposure and incident response complexity.
3
Lateral reach — past segmentation narrative 3
Attacker
I execute arbitrary JavaScript in the victim's browser session to steal credentials, session tokens, or sensitive personal information.
Business
Customer trust erodes as user data is exfiltrated; regulatory compliance obligations increase due to unauthorized data access incidents.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by appleCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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