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LibreswanApplication

CVE-2023-38710

MEDIUM · 6.5 CVSS v3.1 Published 2023-08-25
Fix available
A fix is available. Upgrade to 4.12 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

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 · unedited
An issue was discovered in Libreswan before 4.12. When an IKEv2 Child SA REKEY packet contains an invalid IPsec protocol ID number of 0 or 1, an error notify INVALID_SPI is sent back. The notify payload's protocol ID is copied from the incoming packet, but the code that verifies outgoing packets fails an assertion that the protocol ID must be ESP (2) or AH(3) and causes the pluto daemon to crash and restart. NOTE: the earliest affected version is 3.20.

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 confidence

Libreswan before 4.12 has a denial-of-service vulnerability in IKEv2 Child SA REKEY handling. When processing a packet with invalid IPsec protocol ID (0 or 1 instead of valid 2 for ESP or 3 for AH), the code copies the invalid protocol ID into an error INVALID_SPI notify payload. The outbound packet validation then fails an assertion expecting only ESP (2) or AH (3), causing the pluto daemon to crash and restart.

MitigationUpgrade to Libreswan 4.12 or later. If immediate upgrade is not possible, implement network-level filtering to drop malformed IKEv2 REKEY packets with invalid protocol IDs before they reach the VPN gateway.

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
LibreswanApplication
Affected:>= 3.20, < 4.12

CVSS 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
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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 checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Libreswan version
    Run 'ipsec --version' or check the package manager for the installed libreswan version
    Affected if The version is 3.20 or higher but lower than 4.12
  2. Verify IKEv2 is enabled
    Check ipsec.conf for 'ikev2=allow' or 'ikev2=insist' configuration, or check for active IKEv2 connections with 'ipsec status'
    Affected if IKEv2 protocol support is enabled and the system accepts IKEv2 connections
  3. Determine if system is exposed to IKEv2 traffic
    Review firewall and network configuration to confirm UDP ports 500 and 4500 are open to this VPN gateway from untrusted networks
    Affected if The VPN gateway is directly accessible from external networks that could send malformed IKEv2 REKEY packets
  4. Check for pluto daemon crashes
    Review system logs (journalctl, syslog, or /var/log/messages) for pluto daemon restart events or assertion failure messages
    Affected if The pluto daemon has crashed or restarted due to the assertion failure with invalid protocol IDs

A system is affected if it runs Libreswan versions 3.20 through 4.11, has IKEv2 enabled, and is exposed to external IKEv2 traffic where malformed REKEY packets could trigger the crash.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Upgrade available Upgrade to 4.12 or later
Fixed in 4.12
Interim mitigation

Upgrade to Libreswan 4.12 or later. If immediate upgrade is not possible, implement network-level filtering to drop malformed IKEv2 REKEY packets with invalid protocol IDs before they reach the VPN gateway.

Recommended fix High confidence

4.12

  1. 1. Check the currently installed Libreswan version using 'ipsec --version' or your system's package manager.
  2. 2. Back up the current IPSec configuration files (typically in /etc/ipsec.conf and /etc/ipsec.d/).
  3. 3. Upgrade Libreswan to version 4.12 or later using your system's package manager (e.g., 'yum update libreswan' or 'apt-get install libreswan').
  4. 4. Verify the new version is installed: 'ipsec --version'.
  5. 5. Restart the IPSec service: 'systemctl restart ipsec' or 'service ipsec restart'.
  6. 6. Verify the service is running without crashes: 'systemctl status ipsec'.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Libreswan Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-38710 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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