CVE-2021-29418: The netmask package before 2.0.1 for Node.js mishandles certain unexpected characters in an IP address string,

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MEDIUM 5.3REMOTEUPGRADE

CVE-2021-29418 is a medium-severity flaw (CVSS 5.3) affecting netmask. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The netmask package before 2.0.1 for Node.js mishandles certain unexpected characters in an IP address string, such as an octal digit of 9. This (in some situations) allows attackers to bypass access control that is based on IP addresses. NOTE: this issue exists because of an incomplete fix for CVE-2021-28918.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.5% (top 26%)
CISA exploited list	No
Weakness	CWE-20
Published	2021-03-30
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: netmask project

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

Am I affected?

Timeline

2021-03-30 07:15 UTCPublished CVE record published
2026-06-17 03:47 UTCUpdated Record last modified

netmask project netmask UPGRADE

Affected: < 2.0.1

Fixed in: 2.0.1

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls netmask

2. UPGRADE to 2.0.1

npm install netmask@">=2.0.1"

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-2021-29418?

netmask: upgrade to 2.0.1. Exact commands for each OS are on this page.

Is CVE-2021-29418 being exploited?

CVE-2021-29418 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-2021-29418 affect?

CVE-2021-29418 affects netmask. Severity is medium (CVSS 5.3). The netmask package before 2.0.1 for Node.js mishandles certain unexpected characters in an IP address string, such as an octal digit of 9. This (in some situations) allows attackers to bypass access control that is based on IP addresses. N

How urgent is CVE-2021-29418?

Priority 42/100. Remotely exploitable, no login, no user action

Software pages

Node.js vulnerabilities

Related CVEs

CVE-2021-28918 CRITICAL 9.1 UPGRADE Improper input validation of octal strings in netmask npm package v1.0.6 and below allows unauthenticated remo

References

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