CVE-2026-56003: A heap buffer overflow due to missing size checking in the property buffer when parsing PCF files in libXfont2

Routine

HIGH 8.5UPGRADE

CVE-2026-56003 is a high-severity flaw (CVSS 8.5) affecting libxfont. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A heap buffer overflow due to missing size checking in the property buffer when parsing PCF files in libXfont2 ComputeScaledProperties() before libXfont2 before 2.0.8 could be used by attackers using authenticated X clients to execute code within the X server.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.5 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 66%)
CISA exploited list	No
Weakness	CWE-122
Published	2026-07-08
Last modified	2026-10-25

Publisher (CNA): SUSE · Vendor: x

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-08 10:16 UTCPublished CVE record published
2026-10-25 20:10 UTCUpdated Record last modified

x libxfont UPGRADE

Affected: >= 2.0.0 and < 2.0.8

Fixed in: 2.0.8

Safe to downgrade to: a release before 2.0.0

1. Check installed version

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

2. UPGRADE to 2.0.8 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libxfont

Note

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

3. If no update is available yet, DOWNGRADE to a release before 2.0.0 (Debian / Ubuntu)

apt-cache madison libxfont sudo apt install libxfont=<VERSION_BEFORE_2.0.0> sudo apt-mark hold libxfont

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list libxfont sudo dnf downgrade libxfont-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add libxfont

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2026-56003?

libxfont: upgrade to 2.0.8. Exact commands for each OS are on this page.

Is CVE-2026-56003 being exploited?

CVE-2026-56003 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-2026-56003 affect?

CVE-2026-56003 affects libxfont. Severity is high (CVSS 8.5). A heap buffer overflow due to missing size checking in the property buffer when parsing PCF files in libXfont2 ComputeScaledProperties() before libXfont2 before 2.0.8 could be used by attackers using authenticated X clients to execute code

How urgent is CVE-2026-56003?

Priority 38/100. High severity

Related CVEs

CVE-2026-56002 HIGH 8.5 UPGRADE A heap bufferflow in pcfReadFont() due to missing glyph bounds checking in libXfont2 before 2.0.8 allows atta
CVE-2026-56001 HIGH 8.5 UPGRADE A heap buffer overflow in BitmapScaleBitmaps in libXfont2 before 2.0.8 due to an overflowing 32bit size could

References

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