CVE-2004-0400: Stack-based buffer overflow in Exim 4 before 4.33, when the headers_check_syntax option is enabled, allows rem

Q: How do I fix CVE-2004-0400?

exim: upgrade to newer than 4.32. Exact commands for each OS are on this page.

Q: Is CVE-2004-0400 being exploited?

CVE-2004-0400 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2004-0400 affect?

CVE-2004-0400 affects exim. Severity is high (CVSS 7.5). Stack-based buffer overflow in Exim 4 before 4.33, when the headers_check_syntax option is enabled, allows remote attackers to cause a denial of service and possibly execute arbitrary code during the header check.

Q: How urgent is CVE-2004-0400?

Priority 55/100. High severity; EPSS top 6%: very likely to be exploited; Public exploit reference

This month

HIGH 7.5UPGRADE

CVE-2004-0400 is a high-severity flaw (CVSS 7.5) affecting exim. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Stack-based buffer overflow in Exim 4 before 4.33, when the headers_check_syntax option is enabled, allows remote attackers to cause a denial of service and possibly execute arbitrary code during the header check.

Why this priority

High severity
EPSS top 6%: very likely to be exploited
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	7.0% (top 6%)
CISA exploited list	No
Published	2004-07-07
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: university of cambridge

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

Am I affected?

Timeline

2004-07-07 04:00 UTCPublished CVE record published
2026-06-16 22:05 UTCUpdated Record last modified

university of cambridge exim UPGRADE

Affected: <= 4.32

Fixed in: newer than 4.32

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 4.32 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade exim

Note

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

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-2004-0400?

exim: upgrade to newer than 4.32. Exact commands for each OS are on this page.

Is CVE-2004-0400 being exploited?

CVE-2004-0400 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-2004-0400 affect?

CVE-2004-0400 affects exim. Severity is high (CVSS 7.5). Stack-based buffer overflow in Exim 4 before 4.33, when the headers_check_syntax option is enabled, allows remote attackers to cause a denial of service and possibly execute arbitrary code during the header check.

How urgent is CVE-2004-0400?

Priority 55/100. High severity; EPSS top 6%: very likely to be exploited; Public exploit reference

Software pages

Exim vulnerabilities

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References

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