Threats / Apple / CVE-2021-30663
CVE-2021-30663
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Apple Multiple Products vulnerability
Integer overflow in WebKit affects Apple iOS, iPadOS, macOS, tvOS, and Safari. Processing maliciously crafted web content can lead to code execution.
Verdict
Today item — known-exploited.
An integer overflow vulnerability in WebKit's HTML parsing enables remote code execution through malicious web content. The vulnerability affects multiple Apple platforms and third-party products using WebKit, with active exploitation observed in the wild.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
7 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 0.03469 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Apple, Multiple Products. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-20 Improper Input Validation, CWE-190 Integer Overflow — weakness family: Memory safety.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
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 a malicious webpage with specially formatted HTML that triggers an integer overflow in WebKit's parser.
Business
Users visiting untrusted websites face arbitrary code execution risk without user interaction beyond normal browsing.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I host the malicious content on a website or distribute it via email, social engineering, or compromised legitimate sites.
Business
Attack surface expands across web browsing, email clients, and any application embedding WebKit for content rendering.
3
Lateral reach — past segmentation narrative 3
Attacker
I achieve code execution within the browser or application context when the victim's device processes the malicious HTML.
Business
Attackers gain ability to steal credentials, install malware, exfiltrate data, or pivot to other systems on the network.
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