High resource usage when parsing multipart form data with many fields
Werkzeug's multipart form data parser will parse an unlimited number of parts, including file parts. Parts can be a small amount of bytes, but each requires CPU time to parse and may use more memory as Python data. If a request can be made to an endpoint that accesses request.data, request.form, request.files, or request.get_data(parse_form_data=False), it can cause unexpectedly high resource usage.
This allows an attacker to cause a denial of service by sending crafted multipart data to an endpoint that will parse it. The amount of CPU time required can block worker processes from handling legitimate requests. The amount of RAM required can trigger an out of memory kill of the process. Unlimited file parts can use up memory and file handles. If many concurrent requests are sent continuously, this can exhaust or kill all available workers.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | werkzeug | < 2.2.3 | 2.2.3 |
References
- https://github.com/pallets/werkzeug/commit/517cac5a804e8c4dc4ed038bb20dacd038e7a9f1
- https://github.com/pallets/werkzeug/releases/tag/2.2.3
- https://github.com/pallets/werkzeug/security/advisories/GHSA-xg9f-g7g7-2323
- https://nvd.nist.gov/vuln/detail/CVE-2023-25577
- https://github.com/pallets/werkzeug
- https://github.com/pypa/advisory-database/tree/main/vulns/werkzeug/PYSEC-2023-58.yaml
- https://security.netapp.com/advisory/ntap-20230818-0003
- https://www.debian.org/security/2023/dsa-5470
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400, CWE-770- Platform
- Python (PyPI)
- Package
werkzeug- Disclosed
- 14.02.2023
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2023-58 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-xg9f-g7g7-2323 - CC BY 4.0
Vulnerability history: werkzeug
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 15
- First → latest
- 10.2017 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 4
- Medium 9
- Low 1
- Unrated 1
Disclosures per year
- 2017: 1
- 2018: 0
- 2019: 1
- 2020: 1
- 2021: 0
- 2022: 2
- 2023: 3
- 2024: 3
- 2025: 1
- 2026: 3
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High resource usage when parsing multipart form data with many fields this entry
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