CVE-2003-1491: Kerio Personal Firewall (KPF) 2.1.4 has a default rule to accept incoming packets from DNS (UDP port 53), whic

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HIGH 7.5DOWNGRADE

CVE-2003-1491 is a high-severity flaw (CVSS 7.5) affecting personal firewall. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Kerio Personal Firewall (KPF) 2.1.4 has a default rule to accept incoming packets from DNS (UDP port 53), which allows remote attackers to bypass the firewall filters via packets with a source port of 53.

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	2.4% (top 16%)
CISA exploited list	No
Weakness	CWE-16, CWE-94
Published	2003-12-31
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: kerio

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

Am I affected?

Timeline

2003-12-31 05:00 UTCPublished CVE record published
2026-06-16 22:04 UTCUpdated Record last modified

kerio personal firewall DOWNGRADE

Affected: 2.1.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.1.4

1. Check installed version

apt-cache policy personal-firewall || rpm -q personal-firewall || personal-firewall --version

2. No fixed release: DOWNGRADE to a release before 2.1.4 (Debian / Ubuntu)

apt-cache madison personal-firewall sudo apt install personal-firewall=<VERSION_BEFORE_2.1.4> sudo apt-mark hold personal-firewall

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

dnf --showduplicates list personal-firewall sudo dnf downgrade personal-firewall-<VERSION_BEFORE_2.1.4> sudo dnf versionlock add personal-firewall

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-2003-1491?

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

Is CVE-2003-1491 being exploited?

CVE-2003-1491 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-2003-1491 affect?

CVE-2003-1491 affects personal firewall. Severity is high (CVSS 7.5). Kerio Personal Firewall (KPF) 2.1.4 has a default rule to accept incoming packets from DNS (UDP port 53), which allows remote attackers to bypass the firewall filters via packets with a source port of 53.

How urgent is CVE-2003-1491?

Priority 47/100. High severity

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References

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