CVE-2021-45487: In NetBSD through 9.2, the IPv4 ID generation algorithm does not use appropriate cryptographic measures.

Q: How do I fix CVE-2021-45487?

netbsd: upgrade to newer than 9.2. Exact commands for each OS are on this page.

Q: Is CVE-2021-45487 being exploited?

CVE-2021-45487 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-45487 affect?

CVE-2021-45487 affects netbsd. Severity is high (CVSS 7.5). In NetBSD through 9.2, the IPv4 ID generation algorithm does not use appropriate cryptographic measures.

Q: How urgent is CVE-2021-45487?

Priority 47/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2021-45487 is a high-severity flaw (CVSS 7.5) affecting netbsd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In NetBSD through 9.2, the IPv4 ID generation algorithm does not use appropriate cryptographic measures.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-330
Published	2021-12-25
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: netbsd

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-12-25 02:15 UTCPublished CVE record published
2026-06-17 04:13 UTCUpdated Record last modified

netbsd netbsd UPGRADE

Affected: <= 9.2

Fixed in: newer than 9.2

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-45487?

netbsd: upgrade to newer than 9.2. Exact commands for each OS are on this page.

Is CVE-2021-45487 being exploited?

CVE-2021-45487 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-45487 affect?

CVE-2021-45487 affects netbsd. Severity is high (CVSS 7.5). In NetBSD through 9.2, the IPv4 ID generation algorithm does not use appropriate cryptographic measures.

How urgent is CVE-2021-45487?

Priority 47/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-45489 HIGH 7.5 UPGRADE In NetBSD through 9.2, the IPv6 Flow Label generation algorithm employs a weak cryptographic PRNG.
CVE-2021-45488 HIGH 7.5 UPGRADE In NetBSD through 9.2, there is an information leak in the TCP ISN (ISS) generation algorithm.
CVE-2021-45484 HIGH 7.5 UPGRADE In NetBSD through 9.2, the IPv6 fragment ID generation algorithm employs a weak cryptographic PRNG.
CVE-2020-26139 MEDIUM 5.3 MITIGATE MITIGATE An issue was discovered in the kernel in NetBSD 7.1
CVE-2012-5365 HIGH 7.5 UPGRADE UPGRADE The IPv6 implementation in FreeBSD and NetBSD (unknown versions, year 2012 and earlier) allows remote attacker

References

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