Starlette has possible denial-of-service vector when parsing large files in multipart forms
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: 6 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-770.
Summary
Starlette is a lightweight ASGI (Asynchronous Server Gateway Interface) framework/toolkit, designed for building async web services in Python. In versions 0.47.1 and below, when parsing a multi-part form with large files (greater than the default max spool size) starlette will block the main thread to roll the file over to disk. This blocks the event thread which means the application can't accept new connections. The UploadFile code has a minor bug where instead of just checking for self._in_memory, the logic should also check if the additional bytes will cause a rollover. The vulnerability is fixed in version 0.47.2.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- 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 |
|---|---|---|---|---|---|
| encode | starlette | before 0.47.2 | 0.47.2 | Patch available | CNA |
| — | starlette (PyPI) | before 0.47.2 | 0.47.2 | Patch available | GHSA-2c2j-9gv5-cj73 |
- starlette Vendorencode Affected before 0.47.2 Fixed in 0.47.2 Patch available CNA
- starlette (PyPI) Vendor— Affected before 0.47.2 Fixed in 0.47.2 Patch available GHSA-2c2j-9gv5-cj73
Remediation
- Fix · CNA starlette (encode) Fixed in 0.47.2
- Fix · GHSA-2c2j-9gv5-cj73 starlette (PyPI) Fixed in 0.47.2 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| 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) | 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-2025-54121
- 2026-10-03 Alias added: GHSA-2c2j-9gv5-cj73
- 2026-10-23 EPSS moved to the 50th–90th percentile
References
Other 5
- https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73
- https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1
- https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14
- https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403
- https://github.com/encode/starlette
More encode vulnerabilities
- TI-2026-35991 Starlette has missing Host header validation that poisons request.url.path, bypassing path-based security checks KEVCVSS 3.1MEDIUM 6.5
- TI-2024-32128 Starlette Denial of service (DoS) via multipart/form-data CVSS 4.0HIGH 8.7
- TI-2026-78981 Django REST framework Accept header parsing causes excessive CPU use CVSS 3.1HIGH 7.5
- TI-2026-78978 Django REST framework JSONParser accepts attacker-chosen codecs CVSS 3.1HIGH 7.5
- TI-2024-16279 python-multipart vulnerable to content-type header Regular expression Denial of Service CVSS 3.1HIGH 7.5
- TI-2023-13590 Path traversal in encode Starlette CVSS 3.1HIGH 7.5
Sources
- CVE-2025-54121 · CVE Program
- CVE-2025-54121 · NVD
- FIRST EPSS
- GHSA-2c2j-9gv5-cj73 · GitHub Advisory Database · CC BY 4.0
- CVE-2025-54121 · Red Hat security data · CC BY 4.0
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