How severe is CVE-2026-40347?

CVE-2026-40347 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-40347 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40347?

CVE-2026-40347 affects Fastapiexpert Python-multipart. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40347?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-40347 have an EU (EUVD) identifier?

Yes. CVE-2026-40347 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23615.

When was CVE-2026-40347 published?

CVE-2026-40347 was published on 2026-04-18 and last updated on 2026-06-17.

CVE-2026-40347

CVE-2026-40347 is a medium-severity vulnerability in Fastapiexpert Python-multipart with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (27th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-23615
Weakness: CWE-400
Affected product: Fastapiexpert Python-multipart
Published: 2026-04-18
Last modified: 2026-06-17

Description

Python-Multipart is a streaming multipart parser for Python. Versions prior to 0.0.26 have a denial of service vulnerability when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. Upgrade to version 0.0.26 or later, which skips ahead to the next boundary candidate when processing leading CR/LF data and immediately discards epilogue data after the closing boundary.

Frequently asked questions

What is CVE-2026-40347?: Python-Multipart is a streaming multipart parser for Python. Versions prior to 0.0.26 have a denial of service vulnerability when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. Upgrade to version 0.0.26 or later, which skips ahead to the next boundary candidate when processing leading CR/LF data and immediately discards epilogue data after the closing boundary.
How severe is CVE-2026-40347?: CVE-2026-40347 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-40347 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40347?: CVE-2026-40347 affects Fastapiexpert Python-multipart. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40347?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40347 have an EU (EUVD) identifier?: Yes. CVE-2026-40347 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23615.
When was CVE-2026-40347 published?: CVE-2026-40347 was published on 2026-04-18 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:*

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