CVE-2021-30858Known exploitationNetwork attack vector

Arbitrary code execution via WebKit use-after-free

Published Aug 24, 2021 · Updated Oct 21, 2025

Use-after-free in WebKit in Apple iOS before 14.8 and macOS before 11.6 allows remote attackers to execute code via crafted web content. WebKit can reuse an object after its memory has been freed while processing attacker-controlled web content. Exploitation requires the target to process that content; Apple reported active exploitation, and code runs in the WebKit process context.

CVSS severity8.8
High
EPSS probability13.43%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in WebKit in Apple iOS before 14.8 and macOS before 11.6 allows remote attackers to execute code via crafted web content. WebKit can reuse an object after its memory has been freed while processing attacker-controlled web content. Exploitation requires the target to process that content; Apple reported active exploitation, and code runs in the WebKit process context.

The record

CVE
CVE-2021-30858
Published
Aug 24, 2021
Updated
Oct 21, 2025
Vendor
Apple
Product
iOS
Classifications
CWE-416, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 24, 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 <14.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Apple · iOSversion=unspecified <14.8
Apple · macOSversion=unspecified <11.6

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

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

CWE-416Use After Free
T1203Exploitation for Client Execution

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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