dbcve.org
NetbsdOperating system

CVE-2021-45487

HIGH · 7.5 CVSS v3.1 Published 2021-12-25
Fix available
A fix is available. Upgrade to after 9.2 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 NetBSD through 9.2, the IPv4 ID generation algorithm does not use appropriate cryptographic measures.

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 confidence

The IPv4 identification (ID) field generation in the NetBSD kernel uses a predictable algorithm instead of cryptographically secure random values. This allows remote attackers to conduct traffic analysis, infer internal network state, or potentially inject malicious fragments by guessing ID values.

MitigationApply the vendor patch when available; otherwise implement network-level filtering or traffic analysis countermeasures at perimeter devices to mitigate predictable ID-based attacks.

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
NetbsdOperating system
Affected:<= 9.2

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
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 checks

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

  1. Confirm NetBSD is the operating system
    Run 'uname -a' and verify the operating system name is NetBSD
    Affected if The system is not running NetBSD (this CVE only affects NetBSD)
  2. Check the NetBSD version
    Run 'uname -r' to get the release version, or 'uname -v' to get the version string
    Affected if The version is 9.2 or earlier (e.g., 9.0, 8.x, 7.x)
  3. Verify IPv4 is enabled on the system
    Check for active IPv4 interfaces using 'ifconfig -a' or 'ip addr show', looking for inet (IPv4) addresses configured
    Affected if No IPv4 interfaces are configured or IPv4 is completely disabled (the vulnerability only affects IPv4 traffic)
  4. Check if the system processes external IPv4 traffic
    Review firewall rules ('ipfstat' or 'pfctl -sr' on NetBSD) or network configuration to determine if the system routes, forwards, or processes IPv4 packets from other hosts
    Affected if The system handles IPv4 traffic from untrusted sources (the vulnerability enables analysis of outbound IPv4 fragments from this host)

You are affected if the system runs NetBSD version 9.2 or earlier and has IPv4 interfaces configured or processes IPv4 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 a release after 9.2
Interim mitigation

Apply the vendor patch when available; otherwise implement network-level filtering or traffic analysis countermeasures at perimeter devices to mitigate predictable ID-based attacks.

Fix this in Netbsd Scoped from the published advisory
  • Consultation4.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,960.

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-2021-45487 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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