CVE-2006-3740: Integer overflow in the scan_cidfont function in X.Org 6.8.2 and XFree86 X server allows local users to execut

Routine

HIGH 7.2DOWNGRADEMITIGATE

CVE-2006-3740 is a high-severity flaw (CVSS 7.2) affecting x.org, xfree86 x. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Integer overflow in the scan_cidfont function in X.Org 6.8.2 and XFree86 X server allows local users to execute arbitrary code via crafted (1) CMap and (2) CIDFont font data with modified item counts in the (a) begincodespacerange, (b) cidrange, and (c) notdefrange sections.

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.2 (High)
EPSS exploit chance	0.5% (top 56%)
CISA exploited list	No
Published	2006-09-13
Last modified	2026-06-16

Publisher (CNA): Red Hat, Inc. · Vendor: x.org · xfree86 project

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2006-09-13 01:07 UTCPublished CVE record published
2026-06-16 22:27 UTCUpdated Record last modified

x.org x.org DOWNGRADE

Affected: 6.8.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.8.2

1. Check installed version

apt-cache policy x.org || rpm -q x.org || x.org --version

2. No fixed release: DOWNGRADE to a release before 6.8.2 (Debian / Ubuntu)

apt-cache madison x.org sudo apt install x.org=<VERSION_BEFORE_6.8.2> sudo apt-mark hold x.org

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list x.org sudo dnf downgrade x.org-<VERSION_BEFORE_6.8.2> sudo dnf versionlock add x.org

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.

xfree86 project xfree86 x 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 xfree86-x || rpm -q xfree86-x || xfree86-x --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-2006-3740?

x.org: downgrade or apply the listed mitigation; xfree86 x: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2006-3740 being exploited?

CVE-2006-3740 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-2006-3740 affect?

CVE-2006-3740 affects x.org, xfree86 x. Severity is high (CVSS 7.2). Integer overflow in the scan_cidfont function in X.Org 6.8.2 and XFree86 X server allows local users to execute arbitrary code via crafted (1) CMap and (2) CIDFont font data with modified item counts in the (a) begincodespacerange, (b) cidr

How urgent is CVE-2006-3740?

Priority 36/100. High severity

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References

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