What is CVE-2021-32677?

CVE-2021-32677 is a high-severity cross-site request forgery (CSRF) vulnerability in fastapi (pip), affecting versions < 0.65.2. It is fixed in 0.65.2. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.

How severe is CVE-2021-32677?

CVE-2021-32677 has a CVSS score of 8.2 (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 fastapi are affected by CVE-2021-32677?

fastapi (pip) versions < 0.65.2 is affected.

Is there a fix for CVE-2021-32677?

Yes. CVE-2021-32677 is fixed in 0.65.2. Upgrade to this version or later.

Is CVE-2021-32677 exploitable, and should I be worried?

Whether CVE-2021-32677 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-2021-32677 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-2021-32677?

Upgrade fastapi to 0.65.2 or later.

CVE-2021-32677 in fastapi

Q: How severe is CVE-2021-32677?

CVE-2021-32677 has a CVSS score of 8.2 (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 fastapi are affected by CVE-2021-32677?

fastapi (pip) versions < 0.65.2 is affected.

Q: Is there a fix for CVE-2021-32677?

Yes. CVE-2021-32677 is fixed in 0.65.2. Upgrade to this version or later.

Q: Is CVE-2021-32677 exploitable, and should I be worried?

Whether CVE-2021-32677 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-2021-32677 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-2021-32677?

Upgrade fastapi to 0.65.2 or later.

Summary

Cross-Site Request Forgery (CSRF) in FastAPI

Workarounds

It's best to upgrade to the latest FastAPI.

But still, it would be possible to add a middleware or a dependency that checks the content-type header and aborts the request if it is not application/json or another JSON compatible content type.

References

For more information

If you have any questions or comments, write to [email protected]

Impact

FastAPI versions lower than 0.65.2 that used cookies for authentication in path operations that received JSON payloads sent by browsers were vulnerable to a Cross-Site Request Forgery (CSRF) attack.

In versions lower than 0.65.2, FastAPI would try to read the request payload as JSON even if the content-type header sent was not set to application/json or a compatible JSON media type (e.g. application/geo+json).

So, a request with a content type of text/plain containing JSON data would be accepted and the JSON data would be extracted.

But requests with content type text/plain are exempt from CORS preflights, for being considered Simple requests. So, the browser would execute them right away including cookies, and the text content could be a JSON string that would be parsed and accepted by the FastAPI application.

A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.

CVE-2021-32677 has a CVSS score of 8.2 (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 (0.65.2); upgrading removes the vulnerable code path.

Affected versions

fastapi (< 0.65.2)

Security releases

fastapi → 0.65.2 (pip)

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

This is fixed in FastAPI 0.65.2.

The request data is now parsed as JSON only if the content-type header is application/json or another JSON compatible media type like application/geo+json.

Frequently Asked Questions

What is CVE-2021-32677? CVE-2021-32677 is a high-severity cross-site request forgery (CSRF) vulnerability in fastapi (pip), affecting versions < 0.65.2. It is fixed in 0.65.2. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
How severe is CVE-2021-32677? CVE-2021-32677 has a CVSS score of 8.2 (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 fastapi are affected by CVE-2021-32677? fastapi (pip) versions < 0.65.2 is affected.
Is there a fix for CVE-2021-32677? Yes. CVE-2021-32677 is fixed in 0.65.2. Upgrade to this version or later.
Is CVE-2021-32677 exploitable, and should I be worried? Whether CVE-2021-32677 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-2021-32677 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-2021-32677? Upgrade fastapi to 0.65.2 or later.