CVE-2026-40347: Fastapiexpert Python-Multipart

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

Python-Multipart is a streaming multipart parser for Python. Versions prior to 0.0.26 have a denial of service vulnerability when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. Upgrade to version 0.0.26 or later, which skips ahead to the next boundary candidate when processing leading CR/LF data and immediately discards epilogue data after the closing boundary.

Affected products

• Fastapiexpert Python-Multipart: before 0.0.26 (fixed in 0.0.26)

Published 2026-04-18. Last modified 2026-06-17.