Browsers may allow "nameless" cookies that look like =value instead of key=value. A vulnerable browser may allow a compromised application on an adjacent subdomain to exploit this to set a cookie like =Host-test=bad for another subdomain.

Werkzeug <= 2.2.2 will parse the cookie =Host-test=bad as Host-test=bad. If a Werkzeug application is running next to a vulnerable or malicious subdomain which sets such a cookie using a vulnerable browser, the Werkzeug application will see the bad cookie value but the valid cookie key.

A flaw was found in python-werkzeug. Werkzeug is multipart form data parser, that will parse an unlimited number of parts, including file parts. These 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.getdata(parseformdata=False), it can cause unexpectedly high resource usage, allowing 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, and if many concurrent requests are sent continuously, this can exhaust or kill all available workers.

DISPUTED Improper parsing of HTTP requests in Pallets Werkzeug v2.1.0 and below allows attackers to perform HTTP Request Smuggling using a crafted HTTP request with multiple requests included inside the body. NOTE: the vendor's position is that this behavior can only occur in unsupported configurations involving development mode and an HTTP server from outside the Werkzeug project.

Open redirect vulnerability in werkzeug before 0.11.6 via a double slash in the URL.

Pallets Werkzeug before 0.15.3, when used with Docker, has insufficient debugger PIN randomness because Docker containers share the same machine id.

In Pallets Werkzeug before 0.15.5, SharedDataMiddleware mishandles drive names (such as C:) in Windows pathnames.