High [CVE-2026-54283] request.form limits silently ignored for application/x-www-form-urlencoded enable DoS

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. An unauthenticated attacker can exploit this by sending a urlencoded request body with an arbitrarily large number of fields or an oversized field, causing denial of service through resource exhaustion.

This only affects applications that explicitly call request.form() on urlencoded input; JSON-only APIs and services where Starlette is a transitive dependency not used for form parsing are not affected. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Weakness: CWE-770.

Affected products named by the advisory: Red Hat AI Inference Server 3.2; Red Hat AI Inference Server 3.4; Red Hat Ansible Automation Platform 2.6; Red Hat Ansible Automation Platform 2.7; and 8 more.