CVE-2018-4209 [High] | Input Validation Bypass in Safari

CVE-2018-4209 is rated Moderate Risk (64.2/100): CVSS High severity, with medium exploitation likelihood (EPSS 2.06%). EPSS rose +1.40% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.66%	2.06%	+1.40%
2	2026-05-13	0.57%	0.66%	+0.08%
3	2026-01-13	—	0.57%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.66%

2.06%

+1.40%

2026-05-13

0.57%

0.66%

+0.08%

2026-01-13

—

0.57%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
8.8	3.0	HIGH	`CVSS:3.0/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]
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]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

8.8

3.0

HIGH

CVSS:3.0/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]

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]

OS Trackers for CVE-2018-4209

vendor	priority	summary	link
`debian`	unimportant	CVE-2018-4209 unimportant priority: Debian including 1 source packages (webkit2gtk), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2018-4209
`gentoo`	normal	CVE-2018-4209: 1 GLSA(s) (201812-04), 1 atom(s) (net-libs/webkit-gtk); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2018-4209
`ubuntu`	medium	CVE-2018-4209 medium priority: Ubuntu including 5 source packages (qtwebkit, qtwebkit-opensource-src, qtwebkit-source, webkit2gtk, webkitgtk), 79 status rows across 16 suites (bionic, cosmic, disco, eoan, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, trusty, upstream, xenial): DNE 38, ignored 24, released 14, needs-triage 3.	https://ubuntu.com/security/CVE-2018-4209

Affected software / configurations for CVE-2018-4209

Vendor	Product	Version	Raw CPE
apple	safari	< 11.1	cpe:2.3:a:apple:safari::::::::
apple	iphone_os	< 11.3	cpe:2.3:o:apple:iphone_os::::::::
apple	tvos	< 11.3	cpe:2.3:o:apple:tvos::::::::
apple	watchos	< 4.3	cpe:2.3:o:apple:watchos::::::::
apple	icloud	< 7.4	cpe:2.3:a:apple:icloud::::::::
apple	itunes	< 12.7.4	cpe:2.3:a:apple:itunes::::::::
canonical	ubuntu_linux	18.04	cpe:2.3:o:canonical:ubuntu_linux:18.04::::lts:::
webkit	webkitgtk\+	< 2.22.0	cpe:2.3:a:webkit:webkitgtk\+::::::::

References for CVE-2018-4209

URL	Tags
https://security.gentoo.org/glsa/201812-04	Third Party Advisory
https://support.apple.com/HT208693%2C
https://support.apple.com/HT208694	Vendor Advisory
https://support.apple.com/HT208695%2C
https://support.apple.com/HT208696%2C
https://support.apple.com/HT208697%2C
https://support.apple.com/HT208698%2C
https://usn.ubuntu.com/3781-1/	Third Party Advisory
https://support.apple.com/en-us/HT208693	Vendor Advisory
https://support.apple.com/en-us/HT208695	Vendor Advisory
https://support.apple.com/en-us/HT208696	Vendor Advisory
https://support.apple.com/en-us/HT208697	Vendor Advisory
https://support.apple.com/en-us/HT208698	Vendor Advisory

URL

CVE-2018-4209

Exploit prediction scoring system (EPSS) score for CVE-2018-4209

Common vulnerability scoring system (CVSS) metrics for CVE-2018-4209

Weakness enumeration for CVE-2018-4209

OS Trackers for CVE-2018-4209

Affected software / configurations for CVE-2018-4209

References for CVE-2018-4209