CVE-2026-40347
mediumpriority · track · 0EPSS 0.004 · 29 %ileDEEUFRUSEPSS · scored 2026-10-27
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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode
ssvc
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weaknesses
The CWE weakness classes this flaw belongs to.
affected products (5)
Products and version ranges known to be affected.
advisories (5)
Vendor and ecosystem advisories describing this.
- WID-SEC-W-2026-1407IBM App Connect Enterprise Certified Container: Mehrere SchwachstellenDeutsch2026-05-06csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in IBM App Connect Enterprise Certified Container ausnutzen, um beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, Cross-Site-Scripting-Angriffe durchzuführen, Daten zu manipulieren, vertrauliche Informationen offenzulegen oder einen Denial-of-Service-Zustand zu verursachen.
- WID-SEC-W-2026-3046IBM Concert: Mehrere SchwachstellenDeutsch2026-08-26csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in IBM Concert ausnutzen, um beliebigen Programmcode auszuführen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, um Dateien zu manipulieren, um einen Cross-Site Scripting Angriff durchzuführen, um einen SQL-Injection Angriff durchzuführen und um Sicherheitsvorkehrungen zu umgehen.
- GHSA-mj87-hwqh-73pjpython-multipart affected by Denial of Service via large multipart preamble or epilogue data2026-04-15ghsa · osvUS
### Summary A denial of service vulnerability exists when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. ### Details Two inefficient multipart parsing paths could be abused with attacker-controlled input. Before the first multipart boundary, the parser handled leading CR and LF bytes inefficiently while searching for the start of the first part. After the closing boundary, the parser continued processing trailing epilogue data instead of discarding it immediately. As a result, parsing time could grow with the size of crafted data placed before the first boundary or after the closing boundary. ### Impact An attacker can send oversized malformed multipart bodies that consume excessive CPU time during request parsing, reducing request-handling capacity and delaying legitimate requests. This issue degrades availability but does not typically result in a complete denial of service for the entire application. ### Mitigation 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.
- CERTFR-2026-AVI-1385Multiples vulnérabilités dans les produits VMwareFrançais2026-10-26vendor · certfrFR
- PYSEC-2026-3038python-multipart affected by Denial of Service via large multipart preamble or epilogue data2026-07-13vendor · osvUS
### Summary A denial of service vulnerability exists when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. ### Details Two inefficient multipart parsing paths could be abused with attacker-controlled input. Before the first multipart boundary, the parser handled leading CR and LF bytes inefficiently while searching for the start of the first part. After the closing boundary, the parser continued processing trailing epilogue data instead of discarding it immediately. As a result, parsing time could grow with the size of crafted data placed before the first boundary or after the closing boundary. ### Impact An attacker can send oversized malformed multipart bodies that consume excessive CPU time during request parsing, reducing request-handling capacity and delaying legitimate requests. This issue degrades availability but does not typically result in a complete denial of service for the entire application. ### Mitigation 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.
also known as (6)
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sources
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references (6)
External citations — patches, advisories, analysis.
- https://github.com/Kludex/python-multipart/releasesPatchcnnvd
- https://nvd.nist.gov/vuln/detail/CVE-2026-40347cnnvd
- https://github.com/Kludex/python-multipart/releases/tag/0.0.26enisa_euvd
- https://github.com/Kludex/python-multipart/security/advisories/GHSA-mj87-hwqh-73pjenisa_euvd
- https://github.com/Kludex/python-multipart/releases/tag/0.0.26ProductRelease Notesnvd
- https://github.com/Kludex/python-multipart/security/advisories/GHSA-mj87-hwqh-73pjVendor Advisorynvd
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