CVE-2000-0990: cmd5checkpw 0.21 and earlier allows remote attackers to cause a denial of service via an "SMTP AUTH" command w

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HIGH 7.5DOWNGRADE

CVE-2000-0990 is a high-severity flaw (CVSS 7.5) affecting cmd5checkpw. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

cmd5checkpw 0.21 and earlier allows remote attackers to cause a denial of service via an "SMTP AUTH" command with an unknown username.

Why this priority

High severity

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	1.6% (top 24%)
CISA exploited list	No
Published	2000-12-19
Last modified	2026-09-23

Publisher (CNA): MITRE · Vendor: krzysztof dabrowski

Last updated 2026-09-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2000-12-19 05:00 UTCPublished CVE record published
2026-09-23 09:10 UTCUpdated Record last modified

krzysztof dabrowski cmd5checkpw DOWNGRADE

Affected: 0.20 · 0.21

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.20

1. Check installed version

apt-cache policy cmd5checkpw || rpm -q cmd5checkpw || cmd5checkpw --version

2. No fixed release: DOWNGRADE to a release before 0.20 (Debian / Ubuntu)

apt-cache madison cmd5checkpw sudo apt install cmd5checkpw=<VERSION_BEFORE_0.20> sudo apt-mark hold cmd5checkpw

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

dnf --showduplicates list cmd5checkpw sudo dnf downgrade cmd5checkpw-<VERSION_BEFORE_0.20> sudo dnf versionlock add cmd5checkpw

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-2000-0990?

cmd5checkpw: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2000-0990 being exploited?

CVE-2000-0990 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-2000-0990 affect?

CVE-2000-0990 affects cmd5checkpw. Severity is high (CVSS 7.5). cmd5checkpw 0.21 and earlier allows remote attackers to cause a denial of service via an "SMTP AUTH" command with an unknown username.

How urgent is CVE-2000-0990?

Priority 45/100. High severity

Related CVEs

CVE-2005-0580 LOW 2.1 DOWNGRADE cmd5checkpw, when running setuid, does not properly drop privileges before calling the execvp function, which

References

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