# CVE-2023-46136: Pallets Werkzeug denial of service in multipart parser

Source: https://junglewise.ai/threats/cve-2023-46136-pallets-werkzeug-denial-of-service-in-multipart-parser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2023-10-25. Updated: 2026-05-20  
License: CC BY 4.0 with a link back

CVE-2023-46136 · Severity: medium · CVSS 5.7 · Published 2023-10-25

Werkzeug is a widely used library for building web applications in Python. A flaw in how it handles file uploads allows an attacker to send a specially crafted request that consumes excessive CPU and memory. This can slow down or completely crash the web server, preventing legitimate users from accessing the service.

Technologies: [werkzeug (PyPI)](https://junglewise.ai/threats/technologies/werkzeug). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2023-46136 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2023-46136 being exploited in the wild.

**How severe is CVE-2023-46136?** Medium severity, with a CVSS score of 5.7, published 25 October 2023.

**Which products and versions are affected?** werkzeug (PyPI) ECOSYSTEM:introduced=3.0.0,fixed=3.0.1, GIT:introduced=0,fixed=f3c803b3ade485a45f12b6d6617595350c0f03e2,fixed=f2300208d5e2a5076cbbb4c2aad71096fd040ef9|ECOSYSTEM:introduced=0,fixed=2.3.8,introduced=3.0.0,fixed=3.0.1.

**Is there a fix for CVE-2023-46136?** Yes. werkzeug (PyPI): upgrade to 3.0.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2023-46136 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2023-46136?** Check whether you run werkzeug (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- werkzeug (PyPI): upgrade to 3.0.1 or later

  ```sh
  pip install "werkzeug>=3.0.1"
  ```


## Technical details

A denial of service vulnerability exists in the Werkzeug multipart/form-data parser due to inefficient buffer management. When a multipart part begins with a carriage return (CR) or line feed (LF) character followed by a large amount of data without those characters, the parser inefficiently appends chunks to an internal bytearray. This results in quadratic-time complexity for boundary lookups on a growing buffer. An attacker can exploit this by sending crafted multipart data to any endpoint that parses such input, leading to high CPU usage and potential Out-of-Memory (OOM) kills. The issue is fixed in versions 3.0.1 and 2.3.8.

## Affected products

- Pallets Werkzeug >= 3.0.0, < 3.0.1; >= 2.0.0rc1, < 2.3.8

## Identifiers

- CVE-2023-46136
- GHSA-hrfv-mqp8-q5rw
- PYSEC-2023-221

## Timeline

- 2023-10-24: patched: Fixes released in versions 3.0.1 and 2.3.8
- 2023-10-25: disclosed: GitHub Advisory published

## References

- [https://api.github.com/users/psrok1](https://api.github.com/users/psrok1)
- [https://github.com/psrok1](https://github.com/psrok1)
- [https://api.github.com/users/psrok1/gists%7B/gist_id%7D](https://api.github.com/users/psrok1/gists%7B/gist_id%7D)
- [https://api.github.com/users/psrok1/repos](https://api.github.com/users/psrok1/repos)
- [https://avatars.githubusercontent.com/u/8720367?v=4](https://avatars.githubusercontent.com/u/8720367?v=4)
- [https://api.github.com/users/psrok1/events%7B/privacy%7D](https://api.github.com/users/psrok1/events%7B/privacy%7D)

## Related threats

- [Werkzeug path traversal via NUL device with NTFS ADS marker](https://junglewise.ai/threats/cve-2026-102598-werkzeug-is-a-comprehensive-wsgi-web-application-library-prior)
- [PYSEC-2026-2044 - Werkzeug safe_join() allows Windows special device names with compound extensions](https://junglewise.ai/threats/cve-2026-21860-werkzeug-safe-join-allows-windows-special-device-names-with)
- [PYSEC-2026-2045 - Werkzeug safe_join not safe on Windows](https://junglewise.ai/threats/cve-2024-49766-werkzeug-safe-join-not-safe-on-windows)
- [PYSEC-2026-2043 - Werkzeug debugger vulnerable to remote execution when interacting with attacker controlled domain](https://junglewise.ai/threats/cve-2024-34069-werkzeug-debugger-remote-code-execution-via-attacker-controlled)
- [PYSEC-2026-1065 - Pallets Werkzeug vulnerable to Path Traversal](https://junglewise.ai/threats/cve-2019-14322-pallets-werkzeug-vulnerable-to-path-traversal)