Resource exhaustion in Encode Starlette
CVE-2026-54283
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (39.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 39.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- Encode Starlette
- Kludex Starlette — versions >= 0.4.1, < 1.3.1
Weakness classification (CWE)
References
- github.com/Kludex/starlette/security/advisories/GHSA-82w8-qh3p-5jfq (Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-54283?
- CVE-2026-54283 is a high-severity vulnerability in Encode Starlette, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-06-22.
- How severe is CVE-2026-54283?
- High severity. CVSS v3 base score is 7.5 out of 10.