Vulnerability record · CVE-2021-30761 · published 8 September 2021

CVE-2021-30761: Apple iOS WebKit memory corruption allows code execution

Apple · Iphone Os

A memory corruption flaw in Apple's WebKit, addressed through improved state management, affects iOS. Processing maliciously crafted web content can lead to arbitrary code execution, and Apple stated it was aware of a report that the issue may have been actively exploited.

8.8 CVSS 3.1 High CISA KEV since 3 Nov 2021 EPSS 11% · top 4.4% CWE-787 · Out-of-bounds write

8.8CVSS 3.1 base score, v2 6.8

11%EPSS exploitation probability, 30 days

YesIn CISA KEV, fix deadline passed

1Affected product versions listed by NVD

3References

17 Jun 2026Last modified by NVD

Description

A memory corruption issue was addressed with improved state management. This issue is fixed in iOS 12.5.4. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 17 September 2026. Confidence: high.

high priorityCVSS 8.8, confirmed active exploitation per Apple and CISA KEV listing, though exploitation requires user interaction and the affected iOS version is old.

What it is

Impact

An attacker can execute arbitrary code in the context of the affected component by getting a victim to load crafted web content, potentially leading to full compromise of the device.

Attack surface

Reached over the network via maliciously crafted web content rendered by WebKit; no privileges are required but user interaction (loading the content) is needed per the CVSS vector.

Exploitation

Listed in CISA KEV with a 2021-11-03 addition date and an EPSS 30-day probability of roughly 10.5 percent (95th percentile), and Apple acknowledged a report of active exploitation.

What to do

Update to iOS 12.5.4 or later per Apple's advisory HT212548.
Inventory iOS devices and confirm patch status, prioritizing any still running versions below 12.5.4.
Restrict or monitor browsing of untrusted web content on unpatched devices where feasible.
Track CISA KEV remediation due date of 2021-11-17 for any remaining exposed systems.

Detection

Monitor for crashes or abnormal behavior in WebKit/WebContent processes on iOS devices.
Review web proxy or DNS logs for connections to known exploit-hosting or malicious domains.
Correlate endpoint or MDM telemetry for signs of unexpected code execution following web browsing.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Exploitation in the wild

CISA added CVE-2021-30761 to the Known Exploited Vulnerabilities catalog on 3 November 2021 as "Apple iOS WebKit Memory Corruption Vulnerability". Required action: Apply updates per vendor instructions. Federal deadline 17 November 2021.

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

Iphone Os Apple

References

Link	Tags
https://support.apple.com/en-us/HT212548	Release NotesVendor Advisory
https://support.apple.com/en-us/HT212548	Release NotesVendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30761	Third Party AdvisoryUS Government Resource

Track CVE-2021-30761 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-30761), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.