CVE-2026-53537— Python-Multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters
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I. Basic Information for CVE-2026-53537
Vulnerability Information
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Vulnerability Title
Python-Multipart: Content-Disposition parameter smuggling via RFC 2231/5987 extended parameters
Source: NVD (National Vulnerability Database)
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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
输入验证不恰当
Source: NVD (National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Kludex | python-multipart | < 0.0.30 | - |
II. Public POCs for CVE-2026-53537
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|---|
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Other References for CVE-2026-53537 (1)
Same Patch Batch · Kludex · 2026-06-22 · 6 CVEs total
| CVE-2026-53539 | 7.5 HIGH | Python-Multipart: Quadratic-time querystring parsing with semicolon separators causes CPU |
| CVE-2026-54283 | 7.5 HIGH | Starlette: request.form() limits silently ignored for application/x-www-form-urlencoded en |
| CVE-2026-53540 | 3.7 LOW | Python-Multipart: Negative Content-Length in parse_form buffers the entire body in memory |
| CVE-2026-53538 | 3.7 LOW | Python-Multipart: Semicolon treated as querystring field separator enables parameter smugg |
| CVE-2026-54282 | 3.7 LOW | Starlette: Unvalidated request path concatenated into authority poisons request.url.hostna |
IV. Related Vulnerabilities
Same product: python-multipart
- CVE-2026-53540
Python-Multipart: Negative Content-Length in parse_form buff - CVE-2026-53538
Python-Multipart: Semicolon treated as querystring field sep - CVE-2026-53539
Python-Multipart: Quadratic-time querystring parsing with se - CVE-2026-42561
Python-Multipart: Denial of Service via unbounded multipart - CVE-2026-40347
Python-Multipart affected by Denial of Service via large mul
Same vendor: Kludex
- CVE-2026-53540
Python-Multipart: Negative Content-Length in parse_form buff - CVE-2026-53538
Python-Multipart: Semicolon treated as querystring field sep - CVE-2026-53539
Python-Multipart: Quadratic-time querystring parsing with se - CVE-2026-54283
Starlette: request.form() limits silently ignored for applic - CVE-2026-54282
Starlette: Unvalidated request path concatenated into author
Same weakness: CWE-20
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