Background exploitation KEV catalog

CVE-2021-30663

Apple Multiple Products WebKit Integer Overflow Vulnerability

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…

CheckOps priority index

4.4/10 Patch within 7 days

Severity7.8

Probability0.4

Exploitation2/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 3.5% higher than 89.2% of CVEs

CVSS 3.1 7.8 AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:

Exploited for 1,826 days 03 Nov 2021

CISA due date 17 Nov 2021 for US federal agencies

Exploitation probability EPSS · FIRST

EPSS probability (%)Percentile among all CVEs

Exploitation signals 2 / 5

KEV catalog (CISA)03 Nov 2021
Exploited in EUVD (ENISA)03 Nov 2021
Used by ransomwareno
EPSS above 10 %3.5%
No account, over the networkno

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply updates per vendor instructions.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Description ENISA EUVD

Affected products

macOSMultiple Products

Affected versions

unspecified <14.1
unspecified <14.6
unspecified <12.5
unspecified <14.5
unspecified <11.3

Weaknesses (CWE)

CWE-20 CWE-190

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

08 Sept 2021
Published
03 Nov 2021
Exploitation reported (ENISA)
03 Nov 2021
Added to the KEV catalog
17 Nov 2021
CISA remediation due date

References

Other exploited vulnerabilities from the same vendor

CVE-2026-86950Apple Multiple Products Out-of-Bounds Write Vulnerability
6.7 · Actively exploited
CVE-2026-65400Apple macOS Improper Authentication Vulnerability
5.8 · Actively exploited
CVE-2025-43520Apple Multiple Products Classic Buffer Overflow Vulnerability
3.4 · Background exploitation
CVE-2025-43510Apple Multiple Products Improper Locking Vulnerability
4.3 · Background exploitation
CVE-2025-31277Apple Multiple Products Buffer Overflow Vulnerability
5.4 · Background exploitation
CVE-2023-43000Apple Multiple products Use-After-Free Vulnerability
5.4 · Background exploitation