| Name | CVE-2026-53537 |
| 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 ยง4.2 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. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| Debian Bugs | 1140628 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| python-multipart (PTS) | bullseye | 0.0.5-2 | fixed |
| bookworm | 0.0.5-3 | fixed | |
| trixie | 0.0.20-1.1~deb13u1 | vulnerable | |
| forky, sid | 0.0.26-1 | vulnerable |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| python-multipart | source | bullseye | (not affected) | |||
| python-multipart | source | bookworm | (not affected) | |||
| python-multipart | source | (unstable) | (unfixed) | 1140628 |
[trixie] - python-multipart <no-dsa> (Minor issue)
[bookworm] - python-multipart <not-affected> (parse_options_header uses a custom regex with no RFC 2231/5987 decoding; email.message.Message introduced in 0.0.7)
[bullseye] - python-multipart <not-affected> (parse_options_header uses a custom regex with no RFC 2231/5987 decoding; email.message.Message introduced in 0.0.7)
https://github.com/Kludex/python-multipart/security/advisories/GHSA-vffw-93wf-4j4q
Fixed by: https://github.com/Kludex/python-multipart/commit/3506c15ce99cb62faf2d5ceb3c4c1e5800cb843d (0.0.30)