CVE-2021-1818Network attack vector

Remote code execution via ImageIO state mishandling

Published Apr 2, 2021 · Updated Aug 3, 2024

Logic error in ImageIO in Apple iOS, iPadOS, and macOS allows remote attackers to crash applications or execute arbitrary code. ImageIO mishandles internal state while processing attacker-controlled image data; Apple has not disclosed the affected parser path or incorrect state transition. Exploitation requires crafted image data to reach ImageIO, and the bounded outcomes are unexpected application termination or code execution.

CVSS severity9.8
Critical
EPSS probability2.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Logic error in ImageIO in Apple iOS, iPadOS, and macOS allows remote attackers to crash applications or execute arbitrary code. ImageIO mishandles internal state while processing attacker-controlled image data; Apple has not disclosed the affected parser path or incorrect state transition. Exploitation requires crafted image data to reach ImageIO, and the bounded outcomes are unexpected application termination or code execution.

The record

CVE
CVE-2021-1818
Published
Apr 2, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
iOS and iPadOS
Classifications
T1658, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 2, 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 <14.4

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 <14.4; version=unspecified <7.3

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS: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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1658Exploitation for Client Execution
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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