CVE-2015-3204
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedlibreswan 3.9 through 3.12 allows remote attackers to cause a denial of service (daemon restart) via an IKEv1 packet with (1) unassigned bits set in the IPSEC DOI value or (2) the next payload value set to ISAKMP_NEXT_SAK.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidencelibreswan 3.9-3.12 contains a denial of service vulnerability where processing malformed IKEv1 packets with unassigned bits in the IPSEC DOI field or with the next payload set to ISAKMP_NEXT_SAK triggers a condition causing the daemon to restart, allowing remote attackers to repeatedly crash the VPN service.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data= 3.9= 3.10= 3.11= 3.12CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Libreswan versionUse your system's package manager or query the libreswan version (e.g., rpm -q libreswan, dpkg -l libreswan, or ipsec --version)Affected if The installed version is 3.9, 3.10, 3.11, or 3.12
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Determine if IKEv1 is enabledReview the ipsec.conf configuration file for any connections using IKEv1 (look for 'ike=...' or 'keyexchange=ikev1' directives, or connections without explicit IKEv2 specification)Affected if Any IKEv1 connections or profiles are configured and active
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Verify the service is exposed to network trafficCheck if the VPN daemon is listening on UDP ports 500 or 4500, and whether firewall rules or network ACLs permit inbound IKEv1 traffic from untrusted sourcesAffected if The IKEv1 service port is reachable from networks that are not explicitly trusted
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Check for unexpected daemon restartsReview system logs (such as /var/log/messages, /var/log/syslog, or journalctl) for entries indicating pluto or libreswan daemon crashes or restartsAffected if Logs show repeated unexpected daemon restarts, especially in patterns consistent with remote crash attempts
Your environment is affected if you are running Libreswan versions 3.9 through 3.12, have IKEv1 enabled, and the service is reachable from networks that could send malicious IKEv1 packets.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade to libreswan 3.13 or later which contains the fix. If immediate upgrade is not possible, consider firewall rules to limit IKEv1 traffic to trusted sources.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2015-3204 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2015-3204 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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