What is CVE-2021-28918?

CVE-2021-28918 is a critical-severity improper input validation vulnerability in netmask (npm), affecting versions < 1.1.0. It is fixed in 1.1.0. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.

How severe is CVE-2021-28918?

CVE-2021-28918 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of netmask are affected by CVE-2021-28918?

netmask (npm) versions < 1.1.0 is affected.

Is there a fix for CVE-2021-28918?

Yes. CVE-2021-28918 is fixed in 1.1.0. Upgrade to this version or later.

Is CVE-2021-28918 exploitable, and should I be worried?

Whether CVE-2021-28918 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2021-28918 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

CVE-2021-28918 in netmask

Q: How severe is CVE-2021-28918?

CVE-2021-28918 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of netmask are affected by CVE-2021-28918?

netmask (npm) versions < 1.1.0 is affected.

Q: Is there a fix for CVE-2021-28918?

Yes. CVE-2021-28918 is fixed in 1.1.0. Upgrade to this version or later.

Q: Is CVE-2021-28918 exploitable, and should I be worried?

Whether CVE-2021-28918 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2021-28918 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2021-28918?

Upgrade netmask to 1.1.0 or later.

Summary

Improper parsing of octal bytes in netmask

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.

:exclamation: NOTE: The fix for this issue was incomplete. A subsequent fix was made in version 2.0.1 which was assigned CVE-2021-29418 / GHSA-pch5-whg9-qr2r. For complete protection from this vulnerability an upgrade to version 2.0.1 or later is recommended.

Impact

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2021-28918 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.1.0); upgrading removes the vulnerable code path.

Affected versions

netmask (< 1.1.0)

Security releases

netmask → 1.1.0 (npm)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade netmask to 1.1.0 or later to resolve this vulnerability.

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2021-28918? CVE-2021-28918 is a critical-severity improper input validation vulnerability in netmask (npm), affecting versions < 1.1.0. It is fixed in 1.1.0. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
How severe is CVE-2021-28918? CVE-2021-28918 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of netmask are affected by CVE-2021-28918? netmask (npm) versions < 1.1.0 is affected.
Is there a fix for CVE-2021-28918? Yes. CVE-2021-28918 is fixed in 1.1.0. Upgrade to this version or later.
Is CVE-2021-28918 exploitable, and should I be worried? Whether CVE-2021-28918 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2021-28918 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2021-28918? Upgrade netmask to 1.1.0 or later.

Other vulnerabilities in netmask

CVE-IDSeverityPackage summary

CVE-2021-29418Mediumnetmask: netmask npm package mishandles octal input data