CVE-2001-0414: Buffer overflow in ntpd ntp daemon 4.0.99k and earlier (aka xntpd and xntp3) allows remote attackers to cause

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HIGH 10.0UPGRADEDOWNGRADE

CVE-2001-0414 is a high-severity flaw (CVSS 10.0) affecting ntpd, xntp3. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow in ntpd ntp daemon 4.0.99k and earlier (aka xntpd and xntp3) allows remote attackers to cause a denial of service and possibly execute arbitrary commands via a long readvar argument.

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (High)
EPSS exploit chance	91.9% (top 1%)
CISA exploited list	No
Published	2001-06-18
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: dave mills

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

Am I affected?

Timeline

2001-06-18 04:00 UTCPublished CVE record published
2026-06-16 21:54 UTCUpdated Record last modified

dave mills ntpd UPGRADE

Affected: <= 4.0.99k · 4.0.99 · 4.0.99a · 4.0.99b · 4.0.99c · 4.0.99d · 4.0.99e · 4.0.99f

Fixed in: newer than 4.0.99k

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 4.0.99k (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ntpd

Note

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

dave mills xntp3 DOWNGRADE

Affected: 5.93 · 5.93a · 5.93b · 5.93c · 5.93d · 5.93e

Fixed in: no fixed release known

Safe to downgrade to: a release before 5.93

1. Check installed version

apt-cache policy xntp3 || rpm -q xntp3 || xntp3 --version

2. No fixed release: DOWNGRADE to a release before 5.93 (Debian / Ubuntu)

apt-cache madison xntp3 sudo apt install xntp3=<VERSION_BEFORE_5.93> sudo apt-mark hold xntp3

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

dnf --showduplicates list xntp3 sudo dnf downgrade xntp3-<VERSION_BEFORE_5.93> sudo dnf versionlock add xntp3

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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: NTP daemon readvar - Remote Buffer Overflow (Metasploit)
Exploit-DB: NTPd - Remote Buffer Overflow
Exploit-DB: NTPd 4.0.99j-k readvar - Remote Buffer Overflow (Metasploit)
Metasploit: NTP Daemon readvar Buffer Overflow

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-2001-0414?

ntpd: upgrade to newer than 4.0.99k; xntp3: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2001-0414 being exploited?

CVE-2001-0414 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-2001-0414 affect?

CVE-2001-0414 affects ntpd, xntp3. Severity is high (CVSS 10.0). Buffer overflow in ntpd ntp daemon 4.0.99k and earlier (aka xntpd and xntp3) allows remote attackers to cause a denial of service and possibly execute arbitrary commands via a long readvar argument.

How urgent is CVE-2001-0414?

Priority 65/100. Critical severity; EPSS top 1%: very likely to be exploited; Public exploit reference

Related CVEs

CVE-2005-2496 MEDIUM 4.6 UPGRADE The xntpd ntp (ntpd) daemon before 4.2.0b, when run with the -u option and using a string to specify the group

References

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