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

This week

CRITICAL 9.1REMOTEUPGRADE

CVE-2021-28918 is a critical-severity flaw (CVSS 9.1) affecting netmask. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper input validation of octal strings in netmask npm package v1.0.6 and below allows unauthenticated remote attackers to perform indeterminate SSRF, RFI, and LFI attacks on many of the dependent packages. A remote unauthenticated attacker can bypass packages relying on netmask to filter IPs and reach critical VPN or LAN hosts.

Why this priority

Critical severity
EPSS top 3%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	15.0% (top 3%)
CISA exploited list	No
Weakness	CWE-704
Published	2021-04-01
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

2021-04-01 13:15 UTCPublished CVE record published
2026-06-17 03:47 UTCUpdated Record last modified

netmask project netmask UPGRADE

Affected: <= 1.0.6

Fixed in: newer than 1.0.6

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls netmask

2. UPGRADE to newer than 1.0.6

npm install netmask@">1.0.6"

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Nuclei scan template: Netmask NPM Package - Server-Side Request Forgery

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-2021-28918?

netmask: upgrade to newer than 1.0.6. Exact commands for each OS are on this page.

Is CVE-2021-28918 being exploited?

CVE-2021-28918 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-2021-28918 affect?

CVE-2021-28918 affects netmask. Severity is critical (CVSS 9.1). Improper input validation of octal strings in netmask npm package v1.0.6 and below allows unauthenticated remote attackers to perform indeterminate SSRF, RFI, and LFI attacks on many of the dependent packages. A remote unauthenticated attac

How urgent is CVE-2021-28918?

Priority 66/100. Critical severity; EPSS top 3%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

npm packages vulnerabilities

Related CVEs

CVE-2021-29418 MEDIUM 5.3 UPGRADE The netmask package before 2.0.1 for Node.js mishandles certain unexpected characters in an IP address string,

References

← Back to latest CVEs