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FreeBSDOperating system

CVE-2018-6918

HIGH · 7.5 CVSS v3.0 Published 2018-04-04
Fix available
A fix is available. Upgrade to 10.4 / 11.1 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges 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
In FreeBSD before 11.1-STABLE, 11.1-RELEASE-p9, 10.4-STABLE, 10.4-RELEASE-p8 and 10.3-RELEASE-p28, the length field of the ipsec option header does not count the size of the option header itself, causing an infinite loop when the length is zero. This issue can allow a remote attacker who is able to send an arbitrary packet to cause the machine to crash.

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

In FreeBSD's IPsec implementation, the length field of the ipsec option header does not account for the option header's own size. When a crafted packet with length set to zero is received, this calculation error causes an infinite loop in the kernel, resulting in a denial of service (system crash).

MitigationApply the FreeBSD security patches (11.1-RELEASE-p9, 10.4-RELEASE-p8, 10.3-RELEASE-p28 or later) or upgrade to a patched stable release to remediate this vulnerability.

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
FreeBSDOperating system
Affected:>= 10.0, < 10.4>= 11.0, < 11.1

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
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/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. Identify FreeBSD version
    Run 'uname -a' or 'freebsd-version -u' to display the installed FreeBSD version
    Affected if The version is 10.0 through 10.3.x, or 11.0 through 11.0.x (falls within >=10.0,<10.4 or >=11.0,<11.1)
  2. Verify IPsec kernel module is loaded
    Run 'kldstat | grep ipsec' to check if the IPsec kernel module is loaded
    Affected if The ipsec module appears in the output, indicating IPsec is available on the system
  3. Check for active IPsec SAs
    Run 'setkey -DP' to display active IPsec security associations
    Affected if Any IPsec SAs (Security Associations) are listed, meaning IPsec is actively in use
  4. Verify IPsec configuration exists
    Check for /etc/ipsec.conf or run 'ipsec status' if configured
    Affected if An IPsec configuration file exists or IPsec status shows active tunnels
  5. Monitor for IPsec traffic
    Use 'tcpdump -i <interface> -c 10 esp' to capture ESP (IPsec) packets on network interfaces
    Affected if ESP (Encapsulating Security Payload) traffic is observed, indicating the system is processing IPsec packets

A system is affected if it runs a vulnerable FreeBSD version (10.0-10.3.x or 11.0-11.0.x) AND has IPsec enabled or configured to process IPsec traffic.

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.

From vendor data
Upgrade available Upgrade to 10.4 / 11.1 or later
Fixed in 10.411.1
Interim mitigation

Apply the FreeBSD security patches (11.1-RELEASE-p9, 10.4-RELEASE-p8, 10.3-RELEASE-p28 or later) or upgrade to a patched stable release to remediate this vulnerability.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

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Scan for this in your stack

Free · runs locally
dbcve dependency scanner

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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-2018-6918 in production — separate from our analysis above.

No notes yet

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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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data