Vulnerability · Published Jun 22, 2026 · Assigned by GitHub_M
CVE-2026-54283Starlette: request.form() limits silently ignored for application/x-www-form-urlencoded enable DoS
High 7.5
In plain English
A high-severity resource allocation without limits in starlette from Kludex. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | starlette | 0.26.1-1+deb12u2 | DEBIAN-CVE-2026-54283 |
| Debian:13 | starlette | 0.46.1-3+deb13u3 | DEBIAN-CVE-2026-54283 |
| Debian:14 | starlette | 1.3.1-1 | DEBIAN-CVE-2026-54283 |
| PyPI | starlette | 1.3.1 | GHSA-82w8-qh3p-5jfq |
| PyPI | starlette | 1.3.1 | PYSEC-2026-249 |
| Ubuntu:22.04:LTS | starlette | no fix listed | UBUNTU-CVE-2026-54283 |
| Ubuntu:24.04:LTS | starlette | no fix listed | UBUNTU-CVE-2026-54283 |
| Ubuntu:25.10 | starlette | no fix listed | UBUNTU-CVE-2026-54283 |
| Ubuntu:26.04:LTS | starlette | no fix listed | UBUNTU-CVE-2026-54283 |
| Ubuntu:26.10 | starlette | no fix listed | UBUNTU-CVE-2026-54283 |
Affected products (as reported)
Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/Kludex/starlette/security/advisories/GHSA-82w8-qh3p-5jfq x_refsource_CONFIRM