CVE-2004-0399: Stack-based buffer overflow in Exim 3.35, and other versions before 4, when the sender_verify option is true,

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HIGH 7.5DOWNGRADE

CVE-2004-0399 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 3.35, and other versions before 4, when the sender_verify option is true, allows remote attackers to cause a denial of service and possibly execute arbitrary code during sender verification.

Why this priority

High severity
EPSS top 2%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	20.5% (top 2%)
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 DOWNGRADE

Affected: all versions · 3.35

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.35

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.35 (Debian / Ubuntu)

apt-cache madison exim sudo apt install exim=<VERSION_BEFORE_3.35> sudo apt-mark hold exim

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

dnf --showduplicates list exim sudo dnf downgrade exim-<VERSION_BEFORE_3.35> sudo dnf versionlock add exim

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: Exim Sender 3.35 - Verification Remote Stack Buffer Overrun

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-2004-0399?

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

Is CVE-2004-0399 being exploited?

CVE-2004-0399 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-2004-0399 affect?

CVE-2004-0399 affects exim. Severity is high (CVSS 7.5). Stack-based buffer overflow in Exim 3.35, and other versions before 4, when the sender_verify option is true, allows remote attackers to cause a denial of service and possibly execute arbitrary code during sender verification.

How urgent is CVE-2004-0399?

Priority 56/100. High severity; EPSS top 2%: very likely to be exploited; Public exploit reference

Software pages

Exim vulnerabilities

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References

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