Threats / Apple / CVE-2021-1871
CVE-2021-1871
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Apple iOS, iPadOS, and macOS vulnerability
WebKit logic vulnerability in Apple iOS, iPadOS, and macOS allows remote code execution through malicious HTML content, affecting Safari and other WebKit-dependent applications.
Verdict
Today item — known-exploited.
A remote attacker can execute arbitrary code by crafting malicious HTML that exploits a logic flaw in WebKit's parsing. The vulnerability has been observed in active exploitation and affects multiple Apple platforms and third-party products using WebKit.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
2 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 0.0712 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Apple, iOS, iPadOS, and macOS. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-1173 CWE-1173.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
WeaknessCWE-1173 · CWE-1173
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 HTML document designed to trigger the WebKit logic flaw during parsing.
Business
User devices become vectors for code execution without user awareness of the attack mechanism.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I deliver the HTML payload through web browsing, email, or embedded content in applications that parse HTML.
Business
Attack surface expands across Safari, mail clients, and third-party apps relying on WebKit rendering.
3
Lateral reach — past segmentation narrative 3
Attacker
I achieve code execution in the context of the vulnerable application or browser process.
Business
Attacker gains ability to access user data, install malware, or pivot to system-level compromise.
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