CVE-2004-0666: Off-by-one error in the POP3_readmsg function in popclient 3.0b6 allows remote attackers to cause a denial of

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HIGH 7.5DOWNGRADE

CVE-2004-0666 is a high-severity flaw (CVSS 7.5) affecting popclient. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Off-by-one error in the POP3_readmsg function in popclient 3.0b6 allows remote attackers to cause a denial of service (application crash) via an e-mail message with a certain line length, which leads to a buffer overflow.

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	1.7% (top 22%)
CISA exploited list	No
Published	2004-08-06
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: popclient

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

Am I affected?

Timeline

2004-08-06 04:00 UTCPublished CVE record published
2026-06-16 22:06 UTCUpdated Record last modified

popclient popclient DOWNGRADE

Affected: 3.0_b6

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0_b6

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.0_b6 (Debian / Ubuntu)

apt-cache madison popclient sudo apt install popclient=<VERSION_BEFORE_3.0_b6> sudo apt-mark hold popclient

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

dnf --showduplicates list popclient sudo dnf downgrade popclient-<VERSION_BEFORE_3.0_b6> sudo dnf versionlock add popclient

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-2004-0666?

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

Is CVE-2004-0666 being exploited?

CVE-2004-0666 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-2004-0666 affect?

CVE-2004-0666 affects popclient. Severity is high (CVSS 7.5). Off-by-one error in the POP3_readmsg function in popclient 3.0b6 allows remote attackers to cause a denial of service (application crash) via an e-mail message with a certain line length, which leads to a buffer overflow.

How urgent is CVE-2004-0666?

Priority 46/100. High severity

References

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