CVE-2021-32677Network attack vector

CSRF via content-type confusion

Published Jun 9, 2021 · Updated Aug 3, 2024

Cross-Site Request Forgery in FastAPI versions before 0.65.2 allows remote attackers to alter data through cookie-authenticated JSON endpoints via crafted browser requests. FastAPI parsed JSON from text/plain bodies even though that media type avoids CORS preflight, so browsers sent attacker-controlled payloads with ambient cookies to state-changing path operations. Exploitation requires a victim browser already authenticated with cookies and an application endpoint that accepts the affected JSON operation; the issue does not disclose data or interrupt service by itself.

CVSS severity8.1
High
EPSS probability0.78%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-Site Request Forgery in FastAPI versions before 0.65.2 allows remote attackers to alter data through cookie-authenticated JSON endpoints via crafted browser requests. FastAPI parsed JSON from text/plain bodies even though that media type avoids CORS preflight, so browsers sent attacker-controlled payloads with ambient cookies to state-changing path operations. Exploitation requires a victim browser already authenticated with cookies and an application endpoint that accepts the affected JSON operation; the issue does not disclose data or interrupt service by itself.

The record

CVE
CVE-2021-32677
Published
Jun 9, 2021
Updated
Aug 3, 2024
Vendor
Tiangolo
Product
FastAPI
Classifications
CWE-352, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.65.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Tiangolo · FastAPIversion=< 0.65.2

Published CVSS scores

8.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
8.8GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N
5.8NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
5.3GitHub Security AdvisoriesCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-352Cross-Site Request Forgery (CSRF)
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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