CVE-2003-0688: The DNS map code in Sendmail 8.12.8 and earlier, when using the "enhdnsbl" feature, does not properly initiali

This month

MEDIUM 5.0WATCHLISTDOWNGRADEDOWNGRADEMITIGATE

CVE-2003-0688 is a medium-severity flaw (CVSS 5.0) affecting sendmail, sendmail, irix. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The DNS map code in Sendmail 8.12.8 and earlier, when using the "enhdnsbl" feature, does not properly initialize certain data structures, which allows remote attackers to cause a denial of service (process crash) via an invalid DNS response that causes Sendmail to free incorrect data.

Why this priority

On your watchlist

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

Risk facts

CVSS score	5.0 (Medium)
EPSS exploit chance	3.6% (top 11%)
CISA exploited list	No
Published	2003-10-20
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: compaq · freebsd · openbsd · redhat · sendmail · sgi

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

Am I affected?

Timeline

2003-10-20 04:00 UTCPublished CVE record published
2026-06-16 22:02 UTCUpdated Record last modified

redhat sendmail DOWNGRADE

Affected: 8.12.5-7 · 8.12.8-4

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.12.5-7

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 8.12.5-7 (Debian / Ubuntu)

apt-cache madison sendmail sudo apt install sendmail=<VERSION_BEFORE_8.12.5-7> sudo apt-mark hold sendmail

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

dnf --showduplicates list sendmail sudo dnf downgrade sendmail-<VERSION_BEFORE_8.12.5-7> sudo dnf versionlock add sendmail

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.

sendmail sendmail DOWNGRADE

Affected: 8.12.1 · 8.12.2 · 8.12.3 · 8.12.4 · 8.12.5 · 8.12.6 · 8.12.7 · 8.12.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.12.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 8.12.1 (Debian / Ubuntu)

apt-cache madison sendmail sudo apt install sendmail=<VERSION_BEFORE_8.12.1> sudo apt-mark hold sendmail

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

dnf --showduplicates list sendmail sudo dnf downgrade sendmail-<VERSION_BEFORE_8.12.1> sudo dnf versionlock add sendmail

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.

sgi irix MITIGATE

Affected: 6.5.19 · 6.5.20 · 6.5.21

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.5.19

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

compaq tru64 MITIGATE

Affected: 5.0a · 5.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 5.0a

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

freebsd freebsd MITIGATE

Affected: 4.6 · 4.7 · 4.8 · 5.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.6

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

openbsd openbsd MITIGATE

Affected: 3.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.2

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2003-0688?

sendmail: downgrade or apply the listed mitigation; sendmail: downgrade or apply the listed mitigation; irix: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2003-0688 being exploited?

CVE-2003-0688 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-2003-0688 affect?

CVE-2003-0688 affects sendmail, sendmail, irix. Severity is medium (CVSS 5.0). The DNS map code in Sendmail 8.12.8 and earlier, when using the "enhdnsbl" feature, does not properly initialize certain data structures, which allows remote attackers to cause a denial of service (process crash) via an invalid DNS response

How urgent is CVE-2003-0688?

Priority 45/100. On your watchlist

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References

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