CVE-2026-54283
High
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.
SeverityHigh
CVSS7.5
Exploit probability—
ProductEncode Starlette
PublishedJun 22, 2026
First seenJun 22, 2026
Weakness typeCWE-770Allocation of resources without limits
How to fix
Update
- encode starlette1.3.1 or later
- starlette1.3.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| encode starlette | 0.4.1 ≤ v < 1.3.1 | 1.3.1 |
| starlettePyPI | 0.4.1 ≤ v < 1.3.1 | 1.3.1 |
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