CVE-2023-3138: A vulnerability was found in libX11

Q: How do I fix CVE-2023-3138?

libx11: upgrade to 1.8.6; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2023-3138 being exploited?

CVE-2023-3138 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-2023-3138 affect?

CVE-2023-3138 affects libx11, enterprise linux. Severity is high (CVSS 7.5). A vulnerability was found in libX11. The security flaw occurs because the functions in src/InitExt.c in libX11 do not check that the values provided for the Request, Event, or Error IDs are within the bounds of the arrays that those functio

Q: How urgent is CVE-2023-3138?

Priority 55/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2023-3138 is a high-severity flaw (CVSS 7.5) affecting libx11, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A vulnerability was found in libX11. The security flaw occurs because the functions in src/InitExt.c in libX11 do not check that the values provided for the Request, Event, or Error IDs are within the bounds of the arrays that those functions write to, using those IDs as array indexes. They trust that they were called with values provided by an Xserver adhering to the bounds specified in the X11 protocol, as all X servers provided by X.Org do. As

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.7% (top 23%)
CISA exploited list	No
Weakness	CWE-119, CWE-787
Published	2023-06-28
Last modified	2026-06-17

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

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

Am I affected?

Timeline

2023-06-28 21:15 UTCPublished CVE record published
2026-06-17 06:13 UTCUpdated Record last modified

x.org libx11 UPGRADE

Affected: < 1.8.6

Fixed in: 1.8.6

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.8.6 (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.

redhat enterprise linux MITIGATE

Affected: 8.0 · 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

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-2023-3138?

libx11: upgrade to 1.8.6; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-3138 being exploited?

CVE-2023-3138 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-2023-3138 affect?

CVE-2023-3138 affects libx11, enterprise linux. Severity is high (CVSS 7.5). A vulnerability was found in libX11. The security flaw occurs because the functions in src/InitExt.c in libX11 do not check that the values provided for the Request, Event, or Error IDs are within the bounds of the arrays that those functio

How urgent is CVE-2023-3138?

Priority 55/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Related CVEs

CVE-2023-43787 HIGH 7.8 UPGRADE MITIGATE A vulnerability was found in libX11 due to an integer overflow within the XCreateImage() function
CVE-2023-43786 MEDIUM 5.5 UPGRADE MITIGATE A vulnerability was found in libX11 due to an infinite loop within the PutSubImage() function
CVE-2023-43785 MEDIUM 6.5 UPGRADE MITIGATE A vulnerability was found in libX11 due to a boundary condition within the _XkbReadKeySyms() function
CVE-2021-31535 CRITICAL 9.8 UPGRADE UPGRADE LookupCol.c in X.Org X through X11R7.7 and libX11 before 1.7.1 might allow remote attackers to execute arbitra
CVE-2020-14363 HIGH 7.8 UPGRADE MITIGATE An integer overflow vulnerability leading to a double-free was found in libX11

References

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