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

Routine

LOW 3.7REMOTEUPGRADE

CVE-2026-53538 is a low-severity flaw (CVSS 3.7) affecting python-multipart. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 pr

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	3.7 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 83%)
CISA exploited list	No
Weakness	CWE-436, CWE-444
Published	2026-06-22
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: fastapiexpert

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-22 18:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

fastapiexpert python-multipart UPGRADE

Affected: < 0.0.30

Fixed in: 0.0.30

Safe to downgrade to: no unaffected older release

1. Check installed version

pip show python-multipart

2. UPGRADE to 0.0.30

pip install --upgrade "python-multipart>=0.0.30"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-53538?

python-multipart: upgrade to 0.0.30. Exact commands for each OS are on this page.

Is CVE-2026-53538 being exploited?

CVE-2026-53538 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-53538 affect?

CVE-2026-53538 affects python-multipart. Severity is low (CVSS 3.7). 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 Pyth

How urgent is CVE-2026-53538?

Priority 22/100. Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

Related CVEs

CVE-2026-53539 HIGH 7.5 UPGRADE Python-Multipart is a streaming multipart parser for Python
CVE-2026-53540 LOW 3.7 UPGRADE Python-Multipart is a streaming multipart parser for Python
CVE-2026-53537 LOW 3.7 UPGRADE Python-Multipart is a streaming multipart parser for Python

References

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