FreeBSDOperating system
CVE-2018-6923
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 · uneditedIn FreeBSD before 11.1-STABLE, 11.2-RELEASE-p2, 11.1-RELEASE-p13, ip fragment reassembly code is vulnerable to a denial of service due to excessive system resource consumption. This issue can allow a remote attacker who is able to send an arbitrary ip fragments to cause the machine to consume excessive resources.
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 confidenceIn FreeBSD before 11.1-STABLE, 11.2-RELEASE-p2, and 11.1-RELEASE-p13, the IP fragment reassembly code contains a vulnerability that allows a remote attacker to send specially crafted IP fragments causing excessive system resource consumption, leading to denial of 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
FreeBSDOperating system
= 2.2= 3.0= 4.3= 4.4= 4.5= 4.6= 4.7= 4.8= 4.9= 4.10= 4.11= 5.0CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check FreeBSD versionRun 'uname -a' or 'freebsd-version -k' to display the installed FreeBSD version and kernel versionAffected if The version is 11.2-RELEASE-p2, 11.1-RELEASE-p13, or any version before 11.1-STABLE (e.g., 11.0-RELEASE, 10.x, 9.x, etc.)
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Verify IP fragment processing is enabledCheck if the system processes IP fragments by examining network configuration with 'sysctl net.inet.ip.fragment' or reviewing firewall rules that may inspect fragmentsAffected if IP fragment processing is enabled (default behavior in FreeBSD); the vulnerability is in the fragment reassembly code itself, not a specific module
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Identify network exposureReview network interface configuration and firewall rules with 'ipfw list', 'pfctl -sr', or 'iptables -L' to determine if the system accepts external IP trafficAffected if The system has public-facing network interfaces or accepts IP traffic from untrusted sources; the attack requires receiving crafted IP fragments from a remote attacker
The system is affected if it runs any FreeBSD version before 11.1-STABLE, or versions 11.2-RELEASE-p2/11.1-RELEASE-p13, and has network exposure to accept IP fragments from untrusted sources.
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 dataUpdate FreeBSD systems to version 11.1-STABLE, 11.2-RELEASE-p2, 11.1-RELEASE-p13 or later to patch the vulnerable IP fragment reassembly code. Consider implementing rate limiting or filtering for IP fragments at network perimeter devices as a temporary mitigation.
Fix this in FreeBSD
Scoped from the published advisory
- Consultation3.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,832.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-6923 — 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-2018-6923 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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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.
- 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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