CVE-2021-30663: Apple Multiple Products WebKit Integer Overflow Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , 56 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 3.5%
EPSS score, percentile 89.2 of all scored records
- How severe?
- 7.8 High
CVSS v3.1 base score, from CISA's enrichment of the record
- What should I do?
CISA deadline . Apply updates per vendor instructions.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- before 11.3
- before 14.5
- before 12.5
- before 14.6
- before 14.1
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: .
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | before 11.3 |
| Status | Versions |
|---|---|
| Affected | before 14.5 |
| Status | Versions |
|---|---|
| Affected | before 12.5 |
| Status | Versions |
|---|---|
| Affected | before 14.6 |
| Status | Versions |
|---|---|
| Affected | before 14.1 |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
Apple iOS, iPadOS, macOS, tvOS, and Safari WebKit contain an integer overflow vulnerability that leads to code execution when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.
Summary: CISA's KEV catalog, as of .
- CISA added CVE-2021-30663 to its Known Exploited Vulnerabilities (KEV) catalog on 3 Nov 2021.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 17 Nov 2021.
- The CVE record was published on 8 Sep 2021, 56 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 7.8 (High), taken from CISA's enrichment of the record.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 3.5% (percentile 89.2), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
Description
An integer overflow was addressed with improved input validation. This issue is fixed in iOS 14.5.1 and iPadOS 14.5.1, tvOS 14.6, iOS 12.5.3, Safari 14.1.1, macOS Big Sur 11.3.1. Processing maliciously crafted web content may lead to arbitrary code execution.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
Weakness
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| Added to CISA KEV | |
| CISA due date for the required action | |
| CVE record last updated |
References
More exploited Apple vulnerabilities
- CVE-2026-86950: Apple Multiple Products Out-of-Bounds Write Vulnerability
- CVE-2026-65400: Apple macOS Improper Authentication Vulnerability
- CVE-2025-31277: Apple Multiple Products Buffer Overflow Vulnerability
- CVE-2025-43510: Apple Multiple Products Improper Locking Vulnerability
- CVE-2025-43520: Apple Multiple Products Classic Buffer Overflow Vulnerability
- CVE-2021-30952: Apple Multiple Products Integer Overflow or Wraparound Vulnerability