CVE-2021-1789Known exploitationPublic exploitNetwork attack vector

Code execution via stale property enumeration state

Published Apr 2, 2021 · Updated Oct 21, 2025

WebKit type confusion in Apple iOS and iPadOS before 14.4 and macOS Big Sur before 11.2 allows remote attackers to execute code. JavaScriptCore's propertyNameEnumerator caches a structure-property count before a Proxy getPrototypeOf callback can mutate the prototype chain, then uses the stale count for an out-of-bounds read. A user must open attacker-controlled web content; the demonstrated memory-corruption chain turns the read into use-after-free and code execution in the WebKit process.

CVSS severity8.8
High
EPSS probability14.48%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

WebKit type confusion in Apple iOS and iPadOS before 14.4 and macOS Big Sur before 11.2 allows remote attackers to execute code. JavaScriptCore's propertyNameEnumerator caches a structure-property count before a Proxy getPrototypeOf callback can mutate the prototype chain, then uses the stale count for an out-of-bounds read. A user must open attacker-controlled web content; the demonstrated memory-corruption chain turns the read into use-after-free and code execution in the WebKit process.

The record

CVE
CVE-2021-1789
Published
Apr 2, 2021
Updated
Oct 21, 2025
Vendor
Apple
Product
iOS and iPadOS
Classifications
CWE-843, T1203
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; version=unspecified <14.0; version=unspecified <14.4; version=unspecified <7.3

Published CVSS scores

8.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-843Access of Resource Using Incompatible Type ('Type Confusion')
T1203Exploitation for Client Execution

Public exploit references

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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