What is CVE-2021-4279?

CVE-2021-4279 is a high-severity security vulnerability in fast-json-patch (npm), affecting versions < 3.1.1. It is fixed in 3.1.1.

How severe is CVE-2021-4279?

CVE-2021-4279 has a CVSS score of 7.3 (High). 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 fast-json-patch are affected by CVE-2021-4279?

fast-json-patch (npm) versions < 3.1.1 is affected.

Is there a fix for CVE-2021-4279?

Yes. CVE-2021-4279 is fixed in 3.1.1. Upgrade to this version or later.

Is CVE-2021-4279 exploitable, and should I be worried?

Whether CVE-2021-4279 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-2021-4279 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-2021-4279 in fast-json-patch

Q: How severe is CVE-2021-4279?

CVE-2021-4279 has a CVSS score of 7.3 (High). 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 fast-json-patch are affected by CVE-2021-4279?

fast-json-patch (npm) versions < 3.1.1 is affected.

Q: Is there a fix for CVE-2021-4279?

Yes. CVE-2021-4279 is fixed in 3.1.1. Upgrade to this version or later.

Q: Is CVE-2021-4279 exploitable, and should I be worried?

Whether CVE-2021-4279 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-2021-4279 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-2021-4279?

Upgrade fast-json-patch to 3.1.1 or later.

Summary

Starcounter-Jack JSON-Patch Prototype Pollution vulnerability

A vulnerability has been found in Starcounter-Jack JSON-Patch up to 3.1.0 and classified as problematic. This vulnerability affects unknown code. The manipulation leads to improperly controlled modification of object prototype attributes ('prototype pollution'). The attack can be initiated remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 3.1.1 can address this issue. The name of the patch is 7ad6af41eabb2d799f698740a91284d762c955c9. It is recommended to upgrade the affected component. VDB-216778 is the identifier assigned to this vulnerability.

Impact

CVE-2021-4279 has a CVSS score of 7.3 (High). 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 (3.1.1); upgrading removes the vulnerable code path.

Affected versions

fast-json-patch (< 3.1.1)

Security releases

fast-json-patch → 3.1.1 (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 fast-json-patch to 3.1.1 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-2021-4279? CVE-2021-4279 is a high-severity security vulnerability in fast-json-patch (npm), affecting versions < 3.1.1. It is fixed in 3.1.1.
How severe is CVE-2021-4279? CVE-2021-4279 has a CVSS score of 7.3 (High). 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 fast-json-patch are affected by CVE-2021-4279? fast-json-patch (npm) versions < 3.1.1 is affected.
Is there a fix for CVE-2021-4279? Yes. CVE-2021-4279 is fixed in 3.1.1. Upgrade to this version or later.
Is CVE-2021-4279 exploitable, and should I be worried? Whether CVE-2021-4279 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-2021-4279 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-2021-4279? Upgrade fast-json-patch to 3.1.1 or later.