Python-Multipart affected by Denial of Service via large multipart preamble or epilogue data
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Partial Red Hat: 8 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-400.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Kludex | python-multipart | before 0.0.26 | 0.0.26 | Patch available | CNA |
| — | python-multipart (PyPI) | before 0.0.26 | 0.0.26 | Patch available | GHSA-mj87-hwqh-73pj |
- python-multipart VendorKludex Affected before 0.0.26 Fixed in 0.0.26 Patch available CNA
- python-multipart (PyPI) Vendor— Affected before 0.0.26 Fixed in 0.0.26 Patch available GHSA-mj87-hwqh-73pj
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:* | before 0.0.26 | Vulnerable | Fastapiexpert |
- cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:* Versions before 0.0.26 Vulnerable ·Fastapiexpert
Remediation
- Fix · CNA python-multipart (Kludex) Fixed in 0.0.26
- Fix · GHSA-mj87-hwqh-73pj python-multipart (PyPI) Fixed in 0.0.26 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Lightspeed Core | Affected | No fix yet: Fix deferred |
| Migration Toolkit for Applications 8 | Affected | No fix yet: Fix deferred |
| OpenShift Lightspeed | Affected | No fix yet: Fix deferred |
| Red Hat AI Inference Server | Affected | No fix yet: Fix deferred |
| Red Hat Ansible Automation Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux AI (RHEL AI) 3 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet: Fix deferred |
| Red Hat Satellite 6 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-40347
- 2026-10-03 Alias added: GHSA-mj87-hwqh-73pj
References
More Kludex vulnerabilities
- TI-2025-38917 Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse CVSS 3.1HIGH 7.5
- TI-2026-30841 Python-Multipart: Denial of Service via unbounded multipart part headers CVSS 3.1HIGH 7.5
- TI-2024-36140 python-multipart has a Denial of service (DoS) via deformation `multipart/form-data` boundary CVSS 3.1HIGH 7.5
Sources
- CVE-2026-40347 · CVE Program
- CVE-2026-40347 · NVD
- FIRST EPSS
- GHSA-mj87-hwqh-73pj · GitHub Advisory Database · CC BY 4.0
- CVE-2026-40347 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences