CVE-2024-47874: Starlette is an Asynchronous Server Gateway Interface (ASGI) framework/toolkit. Prior to version 0.40.0, Starlette treats `multipart/form-data` parts ...

Description

Starlette is an Asynchronous Server Gateway Interface (ASGI) framework/toolkit. Prior to version 0.40.0, Starlette treats `multipart/form-data` parts without a `filename` as text form fields and buffers those in byte strings with no size limit. This allows an attacker to upload arbitrary large form fields and cause Starlette to both slow down significantly due to excessive memory allocations and copy operations, and also consume more and more memory until the server starts swapping and grinds to a halt, or the OS terminates the server process with an OOM error. Uploading multiple such requests in parallel may be enough to render a service practically unusable, even if reasonable request size limits are enforced by a reverse proxy in front of Starlette. This Denial of service (DoS) vulnerability affects all applications built with Starlette (or FastAPI) accepting form requests. Verison 0.40.0 fixes this issue.

Metrics

CVSS 4.0

8.7/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.65%

46.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-770

References

Timeline

Published: Oct 15, 2024
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2024-47874?

Starlette is an Asynchronous Server Gateway Interface (ASGI) framework/toolkit. Prior to version 0.40.0, Starlette treats `multipart/form-data` parts without a `filename` as text form fields and buffers those in byte strings with no size limit. This allows an attacker to upload arbitrary large form fields and cause Starlette to both slow down significantly due to excessive memory allocations and copy operations, and also consume more and more memory until the server starts swapping and grinds to a halt, or the OS terminates the server process with an OOM error. Uploading multiple such requests in parallel may be enough to render a service practically unusable, even if reasonable request size limits are enforced by a reverse proxy in front of Starlette. This Denial of service (DoS) vulnerability affects all applications built with Starlette (or FastAPI) accepting form requests. Verison 0.40.0 fixes this issue.

How severe is CVE-2024-47874?

CVE-2024-47874 has a CVSS score of 8.7/10 (HIGH severity). The EPSS model estimates a 0.65% probability of exploitation in the next 30 days.

How do I fix CVE-2024-47874?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.