CVE-2021-1817Network attack vector

Arbitrary code execution via WebKit state corruption

Published Sep 8, 2021 · Updated Aug 3, 2024

Memory corruption in Apple WebKit before macOS 11.3, iOS, iPadOS, and tvOS 14.5, and watchOS 7.4 allows remote attackers to execute arbitrary code. WebKit mishandles state while processing attacker-controlled web content, corrupting memory; Apple has not disclosed the affected function or object. A target must process the crafted content; Apple reports arbitrary code execution but provides no further privilege or sandbox details.

CVSS severity8.8
High
EPSS probability1.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Apple WebKit before macOS 11.3, iOS, iPadOS, and tvOS 14.5, and watchOS 7.4 allows remote attackers to execute arbitrary code. WebKit mishandles state while processing attacker-controlled web content, corrupting memory; Apple has not disclosed the affected function or object. A target must process the crafted content; Apple reports arbitrary code execution but provides no further privilege or sandbox details.

The record

CVE
CVE-2021-1817
Published
Sep 8, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
iOS and iPadOS
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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 <14.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Apple · iOS and iPadOSversion=unspecified <14.5
Apple · tvOSversion=unspecified <14.5
Apple · macOSversion=unspecified <11.3
Apple · watchOSversion=unspecified <7.4

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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.

Technologies

Your stack

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Your stack

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