What is CVE-2024-35220?

CVE-2024-35220 is a high-severity security vulnerability in @fastify/session (npm), affecting versions < 10.9.0. It is fixed in 10.9.0.

How severe is CVE-2024-35220?

CVE-2024-35220 has a CVSS score of 7.4 (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 @fastify/session are affected by CVE-2024-35220?

@fastify/session (npm) versions < 10.9.0 is affected.

Is there a fix for CVE-2024-35220?

Yes. CVE-2024-35220 is fixed in 10.9.0. Upgrade to this version or later.

Is CVE-2024-35220 exploitable, and should I be worried?

Whether CVE-2024-35220 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-2024-35220 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-2024-35220?

Upgrade @fastify/session to 10.9.0 or later.

CVE-2024-35220 in @fastify/session

Q: How severe is CVE-2024-35220?

CVE-2024-35220 has a CVSS score of 7.4 (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 @fastify/session are affected by CVE-2024-35220?

@fastify/session (npm) versions < 10.9.0 is affected.

Q: Is there a fix for CVE-2024-35220?

Yes. CVE-2024-35220 is fixed in 10.9.0. Upgrade to this version or later.

Q: Is CVE-2024-35220 exploitable, and should I be worried?

Whether CVE-2024-35220 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-2024-35220 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-2024-35220?

Upgrade @fastify/session to 10.9.0 or later.

Summary

@fastify/session reuses destroyed session cookie

Workarounds

None

References

Publicly reported at: https://github.com/fastify/session/issues/251

Impact

When restoring the cookie from the session store, the expires field is overriden if the maxAge field was set.
This means a cookie is never correctly detected as expired and thus expired sessions are not destroyed.

CVE-2024-35220 has a CVSS score of 7.4 (High). The vector is network-reachable, no 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 (10.9.0); upgrading removes the vulnerable code path.

Affected versions

@fastify/session (< 10.9.0)

Security releases

@fastify/session → 10.9.0 (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

Updating to v10.9.0 will solve this.

Frequently Asked Questions

What is CVE-2024-35220? CVE-2024-35220 is a high-severity security vulnerability in @fastify/session (npm), affecting versions < 10.9.0. It is fixed in 10.9.0.
How severe is CVE-2024-35220? CVE-2024-35220 has a CVSS score of 7.4 (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 @fastify/session are affected by CVE-2024-35220? @fastify/session (npm) versions < 10.9.0 is affected.
Is there a fix for CVE-2024-35220? Yes. CVE-2024-35220 is fixed in 10.9.0. Upgrade to this version or later.
Is CVE-2024-35220 exploitable, and should I be worried? Whether CVE-2024-35220 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-2024-35220 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-2024-35220? Upgrade @fastify/session to 10.9.0 or later.