CVE-2021-45484
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 NetBSD through 9.2, the IPv6 fragment ID generation algorithm employs a weak cryptographic PRNG.
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 confidenceThe IPv6 fragment ID generation in NetBSD up to 9.2 uses a weak cryptographic PRNG, making fragment IDs predictable. This allows remote attackers to potentially predict fragment IDs and conduct fragmentation-based attacks such as packet injection or bypassing security controls.
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<= 9.2CVSS 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
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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 NetBSD versionRun `uname -a` or `cat /etc/release` to determine the installed NetBSD versionAffected if The version is 9.2 or earlier (any version up to and including 9.2)
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Check IPv6 interface statusRun `ifconfig -a` and look for inet6 addresses or IPv6-enabled interfacesAffected if IPv6 is configured on any network interface (this is required for the vulnerability to be exploitable)
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Verify IPv6 routing is enabledCheck if the system has IPv6 routing enabled by examining kernel parameters or network configuration filesAffected if IPv6 routing or forwarding is enabled, indicating the system processes IPv6 traffic
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Check for IPv6 fragmentation handlingMonitor IPv6 traffic with `tcpdump -i <interface> -v` or check if the system handles fragmented IPv6 packetsAffected if The system processes or forwards IPv6 packets that could be fragmented
The system is affected if it runs NetBSD version 9.2 or earlier AND has IPv6 enabled or processes IPv6 traffic, as only then would the predictable fragment ID generation be exploitable.
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.
dbcve · scopedUpgrade to a patched NetBSD version that implements a cryptographically strong PRNG for IPv6 fragment ID generation. If no upgrade is available, implement kernel-level changes to use a stronger random number generator for fragment identification.
NetBSD 9.3 or later
- 1. Check current NetBSD version using 'uname -a' or 'sysctl kern.version'
- 2. Download NetBSD 9.3 or later from the official NetBSD releases (https://www.NetBSD.org/releases/)
- 3. Review the NetBSD 9.3 release notes for security fixes and migration notes
- 4. Plan system backup and maintenance window
- 5. Perform a fresh install or upgrade following the NetBSD upgrade guide (https://www.NetBSD.org/docs/guide/en/)
- 6. After upgrade, verify the kernel version matches the patched release
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation8.0 h
- Testing6.0 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 $4,960.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-45484 — 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-2021-45484 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
- No spam, self-promotion, credentials, or personal data