Vulnerability Description
Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently applies RFC 2231/5987 decoding. The extended parameter syntax (filename*=charset'lang'value, name*=..., and the filename*0/filename*1 continuation form) is decoded and surfaced under the bare filename/name key, and overrides the plain parameter when both are present. RFC 7578 §4.2 explicitly forbids the filename* form in multipart/form-data. Components that follow RFC 7578, or that do not implement RFC 2231/5987 decoding for multipart/form-data (WAFs, proxies, gateways), may interpret such a header differently. An attacker can exploit that difference to smuggle a different field name or filename past an upstream inspector to the backend. This vulnerability is fixed in 0.0.30.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Fastapiexpert | Python-Multipart | < 0.0.30 |
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-53537?
CVE-2026-53537 is a vulnerability with a CVSS score of 3.7 (LOW). Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, parse_options_header parsed Content-Disposition (and Content-Type) headers with email.message.Message, which transparently...
How severe is CVE-2026-53537?
CVE-2026-53537 has been rated LOW with a CVSS base score of 3.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-53537?
Check the references section above for vendor advisories and patch information. Affected products include: Fastapiexpert Python-Multipart.