CVE-2016-4590: WebKit in Apple iOS before 9.3.3 and Safari before 9.1.2 mishandles about: URLs, which allows remote attackers

Q: How do I fix CVE-2016-4590?

safari: upgrade to newer than 9.1.1; webkit: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2016-4590 being exploited?

CVE-2016-4590 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2016-4590 affect?

CVE-2016-4590 affects safari, webkit. Severity is medium (CVSS 5.4). WebKit in Apple iOS before 9.3.3 and Safari before 9.1.2 mishandles about: URLs, which allows remote attackers to bypass the Same Origin Policy via a crafted web site.

Q: How urgent is CVE-2016-4590?

Priority 37/100. No elevated risk signals yet.

Routine

MEDIUM 5.4UPGRADEMITIGATE

CVE-2016-4590 is a medium-severity flaw (CVSS 5.4) affecting safari, webkit. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

WebKit in Apple iOS before 9.3.3 and Safari before 9.1.2 mishandles about: URLs, which allows remote attackers to bypass the Same Origin Policy via a crafted web site.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.5% (top 26%)
CISA exploited list	No
Weakness	CWE-20
Published	2016-07-22
Last modified	2026-06-17

Publisher (CNA): Apple Inc. · Vendor: apple

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2016-07-22 02:59 UTCPublished CVE record published
2026-06-17 00:47 UTCUpdated Record last modified

apple safari UPGRADE

Affected: <= 9.1.1

Fixed in: newer than 9.1.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy safari || rpm -q safari || safari --version

2. UPGRADE to newer than 9.1.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade safari

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade safari

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

apple webkit MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy webkit || rpm -q webkit || webkit --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2016-4590?

safari: upgrade to newer than 9.1.1; webkit: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2016-4590 being exploited?

CVE-2016-4590 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2016-4590 affect?

CVE-2016-4590 affects safari, webkit. Severity is medium (CVSS 5.4). WebKit in Apple iOS before 9.3.3 and Safari before 9.1.2 mishandles about: URLs, which allows remote attackers to bypass the Same Origin Policy via a crafted web site.

How urgent is CVE-2016-4590?

Priority 37/100. No elevated risk signals yet.

Software pages

iOS vulnerabilities · Safari vulnerabilities · WebKit vulnerabilities · Apple Safari and WebKit vulnerabilities

Related CVEs

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CVE-2025-43342 CRITICAL 9.8 UPGRADE UPGRADE A correctness issue was addressed with improved checks
CVE-2025-43343 CRITICAL 9.8 UPGRADE UPGRADE The issue was addressed with improved memory handling
CVE-2025-43376 HIGH 7.5 UPGRADE UPGRADE A logic issue was addressed with improved state management

References

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