CVE-2001-0955: Buffer overflow in fbglyph.c in XFree86 before 4.2.0, related to glyph clipping for large origins, allows atta

Routine

HIGH 7.2DOWNGRADE

CVE-2001-0955 is a high-severity flaw (CVSS 7.2) affecting x11r6. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow in fbglyph.c in XFree86 before 4.2.0, related to glyph clipping for large origins, allows attackers to cause a denial of service and possibly gain privileges via a large number of characters, possibly through the web page search form of KDE Konqueror or from an xterm command with a long title.

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 61%)
CISA exploited list	No
Published	2001-09-22
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: xfree86 project

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

Am I affected?

Timeline

2001-09-22 04:00 UTCPublished CVE record published
2026-06-16 21:55 UTCUpdated Record last modified

xfree86 project x11r6 DOWNGRADE

Affected: 4.0 · 4.0.1 · 4.0.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0

1. Check installed version

apt-cache policy x11r6 || rpm -q x11r6 || x11r6 --version

2. No fixed release: DOWNGRADE to a release before 4.0 (Debian / Ubuntu)

apt-cache madison x11r6 sudo apt install x11r6=<VERSION_BEFORE_4.0> sudo apt-mark hold x11r6

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

dnf --showduplicates list x11r6 sudo dnf downgrade x11r6-<VERSION_BEFORE_4.0> sudo dnf versionlock add x11r6

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-2001-0955?

x11r6: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2001-0955 being exploited?

CVE-2001-0955 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-2001-0955 affect?

CVE-2001-0955 affects x11r6. Severity is high (CVSS 7.2). Buffer overflow in fbglyph.c in XFree86 before 4.2.0, related to glyph clipping for large origins, allows attackers to cause a denial of service and possibly gain privileges via a large number of characters, possibly through the web page se

How urgent is CVE-2001-0955?

Priority 35/100. High severity

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References

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