CVE-2021-1870: Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability

Q: How do I fix CVE-2021-1870?

ipados: upgrade to 14.4; iphone os: upgrade to 14.4; mac os x: upgrade to 10.15.7. Exact commands for each OS are on this page.

Q: Is CVE-2021-1870 being exploited?

Yes. CVE-2021-1870 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

Q: What does CVE-2021-1870 affect?

CVE-2021-1870 affects ipados, iphone os, mac os x. Severity is critical (CVSS 9.8). A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrar

Q: How urgent is CVE-2021-1870?

Priority 91/100. Critical severity; EPSS top 5%: very likely to be exploited; Exploited in the wild (CISA KEV); CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Patch now

CRITICAL 9.8EXPLOITEDREMOTEUPGRADEUPGRADEUPGRADE

CVE-2021-1870 is a critical-severity flaw (CVSS 9.8) affecting ipados, iphone os, mac os x, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

Why this priority

Critical severity
EPSS top 5%: very likely to be exploited
Exploited in the wild (CISA KEV)
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	7.7% (top 5%)
CISA exploited list	Yes, fix due 2021-11-17
Published	2021-04-02
Last modified	2026-06-17

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

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

Am I affected?

Timeline

2021-04-02 19:15 UTCPublished CVE record published
2021-11-03Exploited Added to the CISA Known Exploited Vulnerabilities list
2021-11-17Deadline CISA due date for US federal agencies to patch
2026-06-17 03:32 UTCUpdated Record last modified

apple ipados UPGRADE

Affected: < 14.4

Fixed in: 14.4

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

apple iphone os UPGRADE

Affected: < 14.4

Fixed in: 14.4

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

apple mac os x UPGRADE

Affected: >= 10.15 and < 10.15.7 · 10.15.7 · 10.15.7 security_update_2020-001 · 10.15.7 supplemental_update

Fixed in: 10.15.7

Safe to downgrade to: a release before 10.15

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

apple macos UPGRADE

Affected: >= 11.0.1 and < 11.2

Fixed in: 11.2

Safe to downgrade to: a release before 11.0.1

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

webkitgtk webkitgtk UPGRADE

Affected: < 2.30.6

Fixed in: 2.30.6

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2.30.6 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade webkitgtk

Note

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

fedoraproject fedora MITIGATE

Affected: 32 · 33

Fixed in: no fixed release known

Safe to downgrade to: a release before 32

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · bitcoin-core-selinux · FIXED · 0.3-2.fc46 · FEDORA-2026-51fc806272 · source

sudo dnf upgrade --advisory=FEDORA-2026-51fc806272

Fedora ELN · guestfs-tools · FIXED · 1.57.5-1.eln159 · FEDORA-2026-9577c5ec16 · source

sudo dnf upgrade --advisory=FEDORA-2026-9577c5ec16

Ubuntu 20.04 · webkit2gtk · FIXED · 2.30.6-0ubuntu0.20.04.1

sudo apt update && sudo apt install --only-upgrade webkit2gtk dpkg --compare-versions "$(dpkg-query -W -f='${Version}' webkit2gtk)" ge "2.30.6-0ubuntu0.20.04.1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · webkit2gtk · FIXED · 2.32.0-1ubuntu3

sudo apt update && sudo apt install --only-upgrade webkit2gtk dpkg --compare-versions "$(dpkg-query -W -f='${Version}' webkit2gtk)" ge "2.32.0-1ubuntu3" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.04 · webkit2gtk · FIXED · 2.32.0-1ubuntu3

sudo apt update && sudo apt install --only-upgrade webkit2gtk dpkg --compare-versions "$(dpkg-query -W -f='${Version}' webkit2gtk)" ge "2.32.0-1ubuntu3" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · webkit2gtk · FIXED · 2.30.6-1

sudo apt update && sudo apt install --only-upgrade webkit2gtk dpkg --compare-versions "$(dpkg-query -W -f='${Version}' webkit2gtk)" ge "2.30.6-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · webkit2gtk · FIXED · 2.30.6-1

sudo apt update && sudo apt install --only-upgrade webkit2gtk dpkg --compare-versions "$(dpkg-query -W -f='${Version}' webkit2gtk)" ge "2.30.6-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · wpewebkit · FIXED · 2.30.6-1

sudo apt update && sudo apt install --only-upgrade wpewebkit dpkg --compare-versions "$(dpkg-query -W -f='${Version}' wpewebkit)" ge "2.30.6-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · wpewebkit · FIXED · 2.30.6-1

sudo apt update && sudo apt install --only-upgrade wpewebkit dpkg --compare-versions "$(dpkg-query -W -f='${Version}' wpewebkit)" ge "2.30.6-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 7 Extended Lifecycle Support · webkitgtk4 · FIXED · webkitgtk4-2.48.3-2.el7_9

sudo dnf upgrade --advisory=RHSA-2025:10364 rpm -q webkitgtk4

RHEL 8 · webkit2gtk3 · FIXED · webkit2gtk3-2.32.3-2.el8

sudo dnf upgrade --advisory=RHSA-2021:4381 rpm -q webkit2gtk3

RHEL 6 · webkitgtk · NO FIX YET

RHEL 7 · webkitgtk3 · DEFERRED

RHEL 9 · webkit2gtk3 · NOT AFFECTED

Alpine 3.20 · webkit2gtk · FIXED · webkit2gtk-2.30.6-r0

apk add --upgrade webkit2gtk apk info -v webkit2gtk

Amazon Linux 2 · see advisory · FIXED · ALAS2-2023-2088 · source

sudo yum update --advisory=ALAS2-2023-2088

Verify at the official source NVD · CVE Program · CISA KEV catalog · 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-2021-1870?

ipados: upgrade to 14.4; iphone os: upgrade to 14.4; mac os x: upgrade to 10.15.7. Exact commands for each OS are on this page.

Is CVE-2021-1870 being exploited?

Yes. CVE-2021-1870 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2021-1870 affect?

CVE-2021-1870 affects ipados, iphone os, mac os x. Severity is critical (CVSS 9.8). A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrar

How urgent is CVE-2021-1870?

Priority 91/100. Critical severity; EPSS top 5%: very likely to be exploited; Exploited in the wild (CISA KEV); CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

iOS vulnerabilities · macOS vulnerabilities · WebKit vulnerabilities · Apple Safari and WebKit vulnerabilities · iPadOS vulnerabilities

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References

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