CVE-2003-0161: The prescan() function in the address parser (parseaddr.c) in Sendmail before 8.12.9 does not properly handle

This week

HIGH 10.0DOWNGRADEDOWNGRADEMITIGATE

CVE-2003-0161 is a high-severity flaw (CVSS 10.0) affecting sendmail, sendmail switch, tru64. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The prescan() function in the address parser (parseaddr.c) in Sendmail before 8.12.9 does not properly handle certain conversions from char and int types, which can cause a length check to be disabled when Sendmail misinterprets an input value as a special "NOCHAR" control value, allowing attackers to cause a denial of service and possibly execute arbitrary code via a buffer overflow attack using messages, a different vulnerability than CVE-2002-

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	10.0 (High)
EPSS exploit chance	38.8% (top 1%)
CISA exploited list	No
Published	2003-04-02
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: compaq · hp · sendmail

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

Am I affected?

Timeline

2003-04-02 05:00 UTCPublished CVE record published
2026-06-16 22:01 UTCUpdated Record last modified

sendmail sendmail DOWNGRADE

Affected: 2.6 · 2.6.1 · 2.6.2 · 3.0 · 3.0.1 · 3.0.2 · 3.0.3 · 8.9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.6

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.6 (Debian / Ubuntu)

apt-cache madison sendmail sudo apt install sendmail=<VERSION_BEFORE_2.6> sudo apt-mark hold sendmail

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

dnf --showduplicates list sendmail sudo dnf downgrade sendmail-<VERSION_BEFORE_2.6> 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 switch DOWNGRADE

Affected: 2.1 · 2.1.1 · 2.1.2 · 2.1.3 · 2.1.4 · 2.1.5 · 2.2 · 2.2.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.1 (Debian / Ubuntu)

apt-cache madison sendmail-switch sudo apt install sendmail-switch=<VERSION_BEFORE_2.1> sudo apt-mark hold sendmail-switch

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

dnf --showduplicates list sendmail-switch sudo dnf downgrade sendmail-switch-<VERSION_BEFORE_2.1> sudo dnf versionlock add sendmail-switch

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.

compaq tru64 MITIGATE

Affected: 4.0b · 4.0d · 4.0d_pk9_bl17 · 4.0f · 4.0f_pk6_bl17 · 4.0f_pk7_bl18 · 4.0g · 4.0g_pk3_bl17

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0b

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.

hp hp-ux MITIGATE

Affected: 10.00 · 10.01 · 10.08 · 10.09 · 10.10 · 10.16 · 10.20 · 10.24

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.00

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.

hp hp-ux series 700 MITIGATE

Affected: 10.20

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.20

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.

hp hp-ux series 800 MITIGATE

Affected: 10.20

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.20

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.

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: Sendmail 8.12.8 (BSD) - 'Prescan()' Remote Command Execution
Exploit-DB: Sendmail 8.11.6 - Address Prescan Memory Corruption

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-2003-0161?

sendmail: downgrade or apply the listed mitigation; sendmail switch: downgrade or apply the listed mitigation; tru64: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2003-0161 being exploited?

CVE-2003-0161 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-2003-0161 affect?

CVE-2003-0161 affects sendmail, sendmail switch, tru64. Severity is high (CVSS 10.0). The prescan() function in the address parser (parseaddr.c) in Sendmail before 8.12.9 does not properly handle certain conversions from char and int types, which can cause a length check to be disabled when Sendmail misinterprets an input va

How urgent is CVE-2003-0161?

Priority 65/100. Critical severity; EPSS top 1%: very likely to be exploited; Public exploit reference

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References

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