Low
python-multipart — security advisory
Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, QuerystringParser treated ; as a field separator in application/x-www-form-urlencoded bodies, in addition to &. The WHATWG URL standard, modern browsers, and Python's urllib.parse (since the CVE-2021-23336 fix) treat only & as a separator. This creates a parser differential: the same bytes are tokenized into different fields than a WHATWG compliant intermediary would produce, allowing an attacker to smuggle extra form fields past an upstream body inspecting component. This vulnerability is fixed in 0.0.30.
- Products
- python-multipart
- Affected versions
- 0.0.20-1, 0.0.20-1.1, 0.0.26-1, 0.0.32-1, 0.0.5-2, 0.0.5-2ubuntu0.1~esm1, 0.0.5-3, 0.0.6-1, 0.0.9-1, 0.0.9-1ubuntu0.1~esm1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-53538
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:08 UTC · Revision 1
Source evidence
Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, QuerystringParser treated ; as a field separator in application/x-www-form-urlencoded bodies, in addition to &. The WHATWG URL standard, modern browsers, and Python's urllib.parse (since the CVE-2021-23336 fix) treat only & as a separator. This creates a parser differential: the same bytes are tokenized into different fields than a WHATWG compliant intermediary would produce, allowing an attacker to smuggle extra form fields past an upstream body inspecting component. This vulnerability is fixed in 0.0.30.
osv:UBUNTU-CVE-2026-53538
python-multipart
Fixed versions: Not specified
python-multipart
Fixed versions: Not specified
python-multipart
Fixed versions: Not specified
python-multipart
Fixed versions: Not specified
python-multipart
Fixed versions: Not specified
Complete source record
{
"id": "18ccbc2333537fb31dd376e56d92180309d3c5045907ce0637514eab4248009c",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-53538",
"method": "structured",
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"title": "UBUNTU-CVE-2026-53538",
"summary": "Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, QuerystringParser treated ; as a field separator in application/x-www-form-urlencoded bodies, in addition to &. The WHATWG URL standard, modern browsers, and Python's urllib.parse (since the CVE-2021-23336 fix) treat only & as a separator. This creates a parser differential: the same bytes are tokenized into different fields than a WHATWG compliant intermediary would produce, allowing an attacker to smuggle extra form fields past an upstream body inspecting component. This vulnerability is fixed in 0.0.30.",
"evidence": "osv:UBUNTU-CVE-2026-53538",
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{
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"modified": "2026-10-17T13:00:25.220707117Z",
"provider": "osv",
"upstream": [
"CVE-2026-53538"
],
"references": [
"https://ubuntu.com/security/CVE-2026-53538",
"https://www.cve.org/CVERecord?id=CVE-2026-53538"
]
},
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"evidence": "/upstream"
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},
"source_id": "core-osv",
"document_id": 360519,
"published_at": "2026-06-22T18:16:00+00:00"
}