CVE-2021-45489
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 Flow Label 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 · moderate confidenceNetBSD through version 9.2 contains a vulnerability in its IPv6 Flow Label generation algorithm, which uses a weak cryptographic PRNG. The IPv6 Flow Label is a 20-bit field used to identify packet flows, and insufficient randomness allows attackers to potentially predict or hijack flows.
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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Confirm NetBSD operating systemRun 'uname -a' or 'cat /etc/release' to identify the operating systemAffected if The system is running NetBSD and version is 9.2 or lower
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Check NetBSD versionRun 'uname -r' or 'uname -v' to obtain the exact version numberAffected if Version is 9.2 or any version lower than 9.2 (e.g., 9.1, 9.0, 8.x, etc.)
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Verify IPv6 is enabledRun 'ifconfig -a' or 'sysctl net.inet6' to check for active IPv6 interfaces and IPv6 kernel configurationAffected if IPv6 interfaces are configured or the system has IPv6 support enabled in the kernel
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Inspect IPv6 flow label values (optional)Capture IPv6 packets using 'tcpdump -i <interface> -v ip6' and observe the flow label field in packet headersAffected if Flow labels appear to have low entropy or predictable patterns (though this requires cryptographic analysis)
You are affected if the system runs NetBSD version 9.2 or earlier AND has IPv6 enabled or used, as the weak PRNG in the flow label generation affects all IPv6 traffic from that system.
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 · scopedUpdate NetBSD to a patched version if available. Otherwise, implement network segmentation or filtering to limit exposure to attackers who could exploit predictable flow labels for traffic analysis or flow hijacking.
NetBSD 9.3 or later
- Backup all critical data and system configurations before performing any system update
- Obtain NetBSD 9.3 or later from official NetBSD distribution sites (ftp.netbsd.org)
- Upgrade the NetBSD installation to version 9.3 or newer
- Reboot the system to load the updated kernel
- Verify the running kernel version with 'uname -a' to confirm the upgrade was successful
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,568.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-45489 — 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-2021-45489 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