CVE-2005-3671: The Internet Key Exchange version 1 (IKEv1) implementation in Openswan 2 (openswan-2) before 2.4.4, and freesw

This month

HIGH 7.8DOWNGRADEDOWNGRADEDOWNGRADE

CVE-2005-3671 is a high-severity flaw (CVSS 7.8) affecting frees wan, openswan, openswan. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The Internet Key Exchange version 1 (IKEv1) implementation in Openswan 2 (openswan-2) before 2.4.4, and freeswan in SUSE LINUX 9.1 before 2.04_1.5.4-1.23, allow remote attackers to cause a denial of service via (1) a crafted packet using 3DES with an invalid key length, or (2) unspecified inputs when Aggressive Mode is enabled and the PSK is known, as demonstrated by the PROTOS ISAKMP Test Suite for IKEv1.

Why this priority

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

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

Risk facts

CVSS score	7.8 (High)
EPSS exploit chance	7.5% (top 6%)
CISA exploited list	No
Published	2005-11-18
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: frees wan · openswan · xelerance

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

Am I affected?

Timeline

2005-11-18 21:03 UTCPublished CVE record published
2026-06-16 22:17 UTCUpdated Record last modified

frees wan frees wan DOWNGRADE

Affected: 2.04

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.04

1. Check installed version

apt-cache policy frees-wan || rpm -q frees-wan || frees-wan --version

2. No fixed release: DOWNGRADE to a release before 2.04 (Debian / Ubuntu)

apt-cache madison frees-wan sudo apt install frees-wan=<VERSION_BEFORE_2.04> sudo apt-mark hold frees-wan

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

dnf --showduplicates list frees-wan sudo dnf downgrade frees-wan-<VERSION_BEFORE_2.04> sudo dnf versionlock add frees-wan

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.

openswan openswan DOWNGRADE

Affected: 2.1.1 · 2.1.2 · 2.1.4 · 2.1.5 · 2.1.6 · 2.2 · 2.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.1.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.1.1 (Debian / Ubuntu)

apt-cache madison openswan sudo apt install openswan=<VERSION_BEFORE_2.1.1> sudo apt-mark hold openswan

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

dnf --showduplicates list openswan sudo dnf downgrade openswan-<VERSION_BEFORE_2.1.1> sudo dnf versionlock add openswan

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.

xelerance openswan DOWNGRADE

Affected: 2.4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.4.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.4.0 (Debian / Ubuntu)

apt-cache madison openswan sudo apt install openswan=<VERSION_BEFORE_2.4.0> sudo apt-mark hold openswan

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

dnf --showduplicates list openswan sudo dnf downgrade openswan-<VERSION_BEFORE_2.4.0> sudo dnf versionlock add openswan

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-2005-3671?

frees wan: downgrade or apply the listed mitigation; openswan: downgrade or apply the listed mitigation; openswan: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2005-3671 being exploited?

CVE-2005-3671 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-2005-3671 affect?

CVE-2005-3671 affects frees wan, openswan, openswan. Severity is high (CVSS 7.8). The Internet Key Exchange version 1 (IKEv1) implementation in Openswan 2 (openswan-2) before 2.4.4, and freeswan in SUSE LINUX 9.1 before 2.04_1.5.4-1.23, allow remote attackers to cause a denial of service via (1) a crafted packet using 3D

How urgent is CVE-2005-3671?

Priority 56/100. High severity; EPSS top 6%: very likely to be exploited; Public exploit reference

Related CVEs

CVE-2004-0590 HIGH 10.0 DOWNGRADE DOWNGRADE FreeS/WAN 1.x and 2.x, and other related products including superfreeswan 1.x, openswan 1.x before 1.0.6, open
CVE-2002-0666 MEDIUM 5.0 DOWNGRADE MITIGATE IPSEC implementations including (1) FreeS/WAN and (2) KAME do not properly calculate the length of authenticat

References

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