CVE-2021-1858

Code execution via ImageIO out-of-bounds write

Published Sep 8, 2021 · Updated Aug 3, 2024

Out-of-bounds write in ImageIO in Apple iOS, iPadOS, tvOS, watchOS, and macOS allows attackers to execute code via a crafted image. ImageIO writes beyond a buffer boundary while processing attacker-controlled image data; Apple has not disclosed the affected decoder or operation. Reaching the flaw requires a target application or service to process the crafted image, after which code runs in that process's security context.

CVSS severity7.8
High
EPSS probability1.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in ImageIO in Apple iOS, iPadOS, tvOS, watchOS, and macOS allows attackers to execute code via a crafted image. ImageIO writes beyond a buffer boundary while processing attacker-controlled image data; Apple has not disclosed the affected decoder or operation. Reaching the flaw requires a target application or service to process the crafted image, after which code runs in that process's security context.

The record

CVE
CVE-2021-1858
Published
Sep 8, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
iOS and iPadOS
Classifications
CWE-787, T1203
Attack vector
local
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 vectorlocal
Required privilegesunauthenticated

What is affected?

Apple · iOS and iPadOSversion=unspecified <14.5
Apple · tvOSversion=unspecified <14.5
Apple · macOSversion=unspecified <11.3; version=unspecified <2021
Apple · watchOSversion=unspecified <7.4

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
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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