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HIGH

Werkzeug vulnerable to high resource usage when parsing multipart/form-data containing a large part with CR/LF character at the beginning

Published Oct 24, 2023

Description

Werkzeug is a comprehensive WSGI web application library. In versions on the 3.x branch prior to 3.0.1 and on the 2.x branch prior to 2.3.8, if an upload of a file that starts with CR or LF and then is followed by megabytes of data without these characters: all of these bytes are appended chunk by chunk into internal bytearray and lookup for boundary is performed on growing buffer. 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. This vulnerability has been patched in version 3.0.1 and 2.3.8.

Affected products

Remediation

Red Hat statement

The vulnerability found in python-werkzeug, which lets attackers carry out denial of service attacks by using carefully crafted multipart data, is considered a moderate issue because it could affect system resources and availability. When this vulnerability is exploited, it can cause the CPU to work excessively hard because the parsing mechanism keeps adding data chunks to an internal buffer without checking boundaries properly. This can result in legitimate requests being delayed or denied as worker processes get overloaded, affecting how well the web application performs and responds. While this problem doesn’t directly compromise data integrity or confidentiality, exploiting it can disrupt the availability of the service, which is why it’s seen as a moderate issue.

Metrics

Weaknesses (3)

CWE-400

Uncontrolled Resource Consumption

CWE-407

CWE-787

Out-of-bounds Write

References (12)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner GitHub_M
Published Oct 24, 2023
Updated May 20, 2026
Reserved Oct 16, 2023
Link CVE-2023-46136
CISA Vulnrichment
Updated n/a
NVD
Status Modified
Modified Jun 17, 2026
Link CVE-2023-46136
Red Hat
Severity Moderate
Public date Oct 25, 2023
Links CVE-2023-46136 - Bugzilla
GHSA-HRFV-MQP8-Q5RW