CVE-2026-53540

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Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.31, parse_form() did not validate the Content-

Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.31, parse_form() did not validate the Content-Length header before using it to bound its chunked read of the request body. A negative Content-Length turned the bounded read into a read-until-EOF, so the entire body was loaded into memory in a single read instead of in fixed-size chunks.

This vulnerability is fixed in 0.0.31.

LOW · CVSS 3.7

Monitor

No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence

No Sigma yet — build one → YARA rules0

Look this up elsewhere - one-click external pivots

NVD CVE.org CISA Exploit-DB GitHub PoC VulnCheck KEV GreyNoise

▸ How to read a CVE - triage first, then detect and patch

This page is every public fact about CVE-2026-53540, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.

Triage: should I act now? Four signals, and they are not interchangeable:

CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked. EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal. CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score. Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.

How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.

Then what - two workflows:

Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits. PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.

Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).

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Severity & exploitation scoring

View on NVD →

CVSS base score

3.7

LOWCVSS v3.1 · [email protected]

EPSS exploitation probability

n/a

No EPSS score in our data for this CVE. EPSS is published daily for scored CVEs - a very new, reserved, or rejected CVE may not have one yet.

CVSS metric silhouette

shape grows toward worst-case

SSVC triage · cisa-vulnrichment

Exploitation

none

Automatable

Tech impact

partial

CVSS vector breakdown

Exploitability - how they get in

Attack Vector

Network Adjacent Local Physical

Attack Complexity

Low High

Privileges Required

None Low High

User Interaction

None Required

Scope

Unchanged Changed

Impact - what breaks

Confidentiality

None Low High

Integrity

None Low High

Availability

None Low High

VECTORCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack path

Full kill chain

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ATT&CK techniques

Techniques this CVE enables. Pills with a solid outline are high confidence - named directly in ATT&CK or Nuclei, or human-curated by CTID; the rest are inferred from the weakness type using MITRE's CVE Mapping Methodology and the CWE → CAPEC chain. Broad, generic-weakness guesses are filtered out. A small N× marks a technique that N independent sources agree on.

T1190 · Exploit Public-Facing Application

▤ Build a SIEM detection for these techniques

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Weakness Classification

CWE-1284Improper Validation of Specified Quantity in Input

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Affected Packages

Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.

PyPI python-multipart LOW fixed in 0.0.31

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Related CVEs

CVEs linked to this one by a shared weakness (CWE) or affected product - joins on data already in the engine, with the reason shown per row. Not a guess.

CVE-2008-1440 Microsoft Windows XP SP2 and SP3, and Server 2003 SP1 and SP2, does not properly... same CWE-1284 CVE-2008-2374 src/sdp.c in bluez-libs 3.30 in BlueZ, and other bluez-libs before 3.34 and blue... same CWE-1284 CRITICAL CVE-2009-4488 Varnish 2.0.6 writes data to a log file without sanitizing non-printable charact... 1 same CWE-1284 CRITICAL CVE-2010-3904 The rds_page_copy_user function in net/rds/page.c in the Reliable Datagram Socke... 2 same CWE-1284 HIGH

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References & Sources

Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.

https://github.com/Kludex/python-multipart/security/advisories/GHSA-v9pg-7xvm-68hf