What is CVE-2020-15084?

CVE-2020-15084 is a high-severity incorrect authorization vulnerability in express-jwt (npm), affecting versions <= 5.3.3. It is fixed in 6.0.0. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.

How severe is CVE-2020-15084?

CVE-2020-15084 has a CVSS score of 7.7 (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 express-jwt are affected by CVE-2020-15084?

express-jwt (npm) versions <= 5.3.3 is affected.

Is there a fix for CVE-2020-15084?

Yes. CVE-2020-15084 is fixed in 6.0.0. Upgrade to this version or later.

Is CVE-2020-15084 exploitable, and should I be worried?

Whether CVE-2020-15084 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-2020-15084 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-2020-15084 in express-jwt

Q: How severe is CVE-2020-15084?

CVE-2020-15084 has a CVSS score of 7.7 (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 express-jwt are affected by CVE-2020-15084?

express-jwt (npm) versions <= 5.3.3 is affected.

Q: Is there a fix for CVE-2020-15084?

Yes. CVE-2020-15084 is fixed in 6.0.0. Upgrade to this version or later.

Q: Is CVE-2020-15084 exploitable, and should I be worried?

Whether CVE-2020-15084 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-2020-15084 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-2020-15084?

Upgrade express-jwt to 6.0.0 or later.

Summary

Authorization bypass in express-jwt

Overview

Versions before and including 5.3.3, we are not enforcing the algorithms entry to be specified in the configuration.
When algorithms is not specified in the configuration, with the combination of jwks-rsa, it may lead to authorization bypass.

Am I affected?

You are affected by this vulnerability if all of the following conditions apply:

You are using express-jwt
AND
You do not have algorithms configured in your express-jwt configuration.
AND
You are using libraries such as jwks-rsa as the secret.

How to fix that?

Specify algorithms in the express-jwt configuration. The following is an example of a proper configuration

const checkJwt = jwt({
  secret: jwksRsa.expressJwtSecret({
    rateLimit: true,
    jwksRequestsPerMinute: 5,
    jwksUri: `https://${DOMAIN}/.well-known/jwks.json`
  }),
  // Validate the audience and the issuer.
  audience: process.env.AUDIENCE,
  issuer: `https://${DOMAIN}/`,
  // restrict allowed algorithms
  algorithms: ['RS256']
});

Will this update impact my users?

The fix provided in patch will not affect your users if you specified the algorithms allowed. The patch now makes algorithms a required configuration.

Credit

IST Group

Impact

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2020-15084 has a CVSS score of 7.7 (High). The vector is network-reachable, low privileges required, and user interaction required. 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 (6.0.0); upgrading removes the vulnerable code path.

Affected versions

express-jwt (<= 5.3.3)

Security releases

express-jwt → 6.0.0 (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 express-jwt to 6.0.0 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-2020-15084? CVE-2020-15084 is a high-severity incorrect authorization vulnerability in express-jwt (npm), affecting versions <= 5.3.3. It is fixed in 6.0.0. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
How severe is CVE-2020-15084? CVE-2020-15084 has a CVSS score of 7.7 (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 express-jwt are affected by CVE-2020-15084? express-jwt (npm) versions <= 5.3.3 is affected.
Is there a fix for CVE-2020-15084? Yes. CVE-2020-15084 is fixed in 6.0.0. Upgrade to this version or later.
Is CVE-2020-15084 exploitable, and should I be worried? Whether CVE-2020-15084 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-2020-15084 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-2020-15084? Upgrade express-jwt to 6.0.0 or later.