CVE-2020-14363: An integer overflow vulnerability leading to a double-free was found in libX11

Q: How do I fix CVE-2020-14363?

libx11: upgrade to 1.6.12; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2020-14363 being exploited?

CVE-2020-14363 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-2020-14363 affect?

CVE-2020-14363 affects libx11, fedora. Severity is high (CVSS 7.8). An integer overflow vulnerability leading to a double-free was found in libX11. This flaw allows a local privileged attacker to cause an application compiled with libX11 to crash, or in some cases, result in arbitrary code execution. The hi

Q: How urgent is CVE-2020-14363?

Priority 44/100. High severity; Public exploit reference

This month

HIGH 7.8UPGRADEMITIGATE

CVE-2020-14363 is a high-severity flaw (CVSS 7.8) affecting libx11, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An integer overflow vulnerability leading to a double-free was found in libX11. This flaw allows a local privileged attacker to cause an application compiled with libX11 to crash, or in some cases, result in arbitrary code execution. The highest threat from this flaw is to confidentiality, integrity as well as system availability.

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-190, CWE-416
Published	2020-09-11
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: fedoraproject · x.org

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

Am I affected?

Timeline

2020-09-11 18:15 UTCPublished CVE record published
2026-06-17 02:54 UTCUpdated Record last modified

x.org libx11 UPGRADE

Affected: < 1.6.12

Fixed in: 1.6.12

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libx11 || rpm -q libx11 || libx11 --version

2. UPGRADE to 1.6.12 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libx11

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libx11

Note

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

fedoraproject fedora MITIGATE

Affected: 33

Fixed in: no fixed release known

Safe to downgrade to: a release before 33

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.

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-2020-14363?

libx11: upgrade to 1.6.12; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-14363 being exploited?

CVE-2020-14363 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-2020-14363 affect?

CVE-2020-14363 affects libx11, fedora. Severity is high (CVSS 7.8). An integer overflow vulnerability leading to a double-free was found in libX11. This flaw allows a local privileged attacker to cause an application compiled with libX11 to crash, or in some cases, result in arbitrary code execution. The hi

How urgent is CVE-2020-14363?

Priority 44/100. High severity; Public exploit reference

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References

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