CVE-2021-1879Known exploitationNetwork attack vector

Universal cross-site scripting via object lifetime mismanagement

Published Apr 2, 2021 · Updated Oct 21, 2025

Universal cross-site scripting in Apple iOS, iPadOS, and watchOS WebKit allows remote attackers to cross security origins via crafted web content. WebKit mishandles object lifetimes while processing attacker-controlled content, allowing script from one origin to execute in another; Apple has not disclosed the affected function or object type. A user must process the malicious content, after which the script can read or alter data exposed to the compromised web origin.

CVSS severity6.1
Medium
EPSS probability7.08%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Universal cross-site scripting in Apple iOS, iPadOS, and watchOS WebKit allows remote attackers to cross security origins via crafted web content. WebKit mishandles object lifetimes while processing attacker-controlled content, allowing script from one origin to execute in another; Apple has not disclosed the affected function or object type. A user must process the malicious content, after which the script can read or alter data exposed to the compromised web origin.

The record

CVE
CVE-2021-1879
Published
Apr 2, 2021
Updated
Oct 21, 2025
Vendor
Apple
Product
iOS
Classifications
CWE-79, T1189
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 <12.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Apple · iOSversion=unspecified <12.5
Apple · iOS and iPadOSversion=unspecified <14.4
Apple · watchOSversion=unspecified <7.3

Published CVSS scores

4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

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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