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3.7 Low

CVE-2026-53538 Python-Multipart is a streaming multipart parser for Python

Description

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.

Affected products and versions

Product Affected versions Fixed in
python-multipart 0.0 earliest → < 0.0.30 0.0.30

References

Timeline

  1. Published
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Other CVEs of python-multipart

The 9 CVEs of python-multipart →
CVE-2026-53540 Python-Multipart is a streaming multipart parser for Python 3.7 Low CVE-2026-53537 Python-Multipart is a streaming multipart parser for Python 3.7 Low CVE-2026-53539 Python-Multipart is a streaming multipart parser for Python 7.5 High CVE-2026-42561 Python-Multipart is a streaming multipart parser for Python 7.5 High
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