CVE-2021-1871Known exploitationNetwork attack vector

Unauthenticated code execution via undisclosed WebKit logic

Published Apr 2, 2021 · Updated Oct 21, 2025

A logic issue in WebKit in Apple iOS and iPadOS before 14.4 and macOS before 11.2 allows remote attackers to execute arbitrary code. Apple has disclosed only that WebKit applied insufficient restrictions; no public advisory identifies the affected function, object, or malformed state. No authentication or user interaction is required, and CISA lists the flaw as known exploited; available records do not narrow the resulting code-execution context.

CVSS severity9.8
Critical
EPSS probability7.00%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A logic issue in WebKit in Apple iOS and iPadOS before 14.4 and macOS before 11.2 allows remote attackers to execute arbitrary code. Apple has disclosed only that WebKit applied insufficient restrictions; no public advisory identifies the affected function, object, or malformed state. No authentication or user interaction is required, and CISA lists the flaw as known exploited; available records do not narrow the resulting code-execution context.

The record

CVE
CVE-2021-1871
Published
Apr 2, 2021
Updated
Oct 21, 2025
Vendor
Apple
Product
iOS and iPadOS
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 2, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <14.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Apple · iOS and iPadOSversion=unspecified <14.4
Apple · macOSversion=unspecified <11.2

Published CVSS scores

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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