CVE-2021-30663

Exp

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.

Published: 2021-09-08 Last update: 2025-10-23 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-30663 is rated Critical Active Threat (86.8/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.96%). CISA KEV confirms active exploitation (added 2021-11-03) affecting Apple / Multiple Products. a weakness (CWE-190) Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2021-30663

Name: Apple Multiple Products WebKit Integer Overflow Vulnerability · CISA KEV detail

Exploit added: 2021-11-03

Action due: 2021-11-17

Required action: Apply updates per vendor instructions.

Exploit prediction scoring system (EPSS) score for CVE-2021-30663

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-22 1.20% 0.96% -0.24%
2 2026-05-11 0.68% 1.20% +0.52%
3 2026-04-07 — 0.68% —

Full EPSS history (27 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-30663

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2021-30663

OS Trackers for CVE-2021-30663

vendor priority summary link
alpine — CVE-2021-30663: 1 source package rows (webkit2gtk); 5 state rows across 5 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, edge-community); fixed 5, open 0. https://security.alpinelinux.org/vuln/CVE-2021-30663
debian not yet assigned CVE-2021-30663 not yet assigned priority: Debian including 2 source packages (webkit2gtk, wpewebkit), 10 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 10. https://security-tracker.debian.org/tracker/CVE-2021-30663
gentoo high CVE-2021-30663: 1 GLSA(s) (202202-01), 1 atom(s) (net-libs/webkit-gtk); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-30663
redhat medium — https://access.redhat.com/security/cve/CVE-2021-30663
ubuntu medium CVE-2021-30663 medium priority: Ubuntu including 5 source packages (qtwebkit-opensource-src, qtwebkit-source, webkit2gtk, webkitgtk, wpewebkit), 60 status rows across 12 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, trusty, upstream, xenial): DNE 27, ignored 20, released 10, needs-triage 3. https://ubuntu.com/security/CVE-2021-30663

Affected software / configurations for CVE-2021-30663

Vendor Product Version Raw CPE
apple safari < 14.1.1 cpe:2.3:a:apple:safari:*:*:*:*:*:*:*:*
apple ipados >= 14.0, < 14.5.1 cpe:2.3:o:apple:ipados:*:*:*:*:*:*:*:*
apple iphone_os < 12.5.3 cpe:2.3:o:apple:iphone_os:*:*:*:*:*:*:*:*
apple iphone_os >= 14.0, < 14.5.1 cpe:2.3:o:apple:iphone_os:*:*:*:*:*:*:*:*
apple macos >= 11.0, < 11.3.1 cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
apple tvos < 14.6 cpe:2.3:o:apple:tvos:*:*:*:*:*:*:*:*

References for CVE-2021-30663

URL Tags
https://support.apple.com/en-us/HT212335 Release Notes Vendor Advisory
https://support.apple.com/en-us/HT212336 Release Notes Vendor Advisory
https://support.apple.com/en-us/HT212341 Release Notes Vendor Advisory
https://support.apple.com/en-us/HT212532 Release Notes Vendor Advisory
https://support.apple.com/en-us/HT212534 Release Notes Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30663 Third Party Advisory US Government Resource
cvelogic Threat Intelligence