Debian Security Advisory

DLA-3346-1 python-werkzeug -- LTS security update

Date Reported:
27 Feb 2023
Affected Packages:
Security database references:
In the Debian bugtracking system: Bug 1031370.
In Mitre's CVE dictionary: CVE-2023-23934, CVE-2023-25577.
More information:

Two vulnerabilities were discovered in Werkzeug, a collection of utilities for WSGI (web) applications. An attacker may inject cookies in specific situations, and cause a denial of service (DoS).

  • CVE-2023-23934

    Werkzeug 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. 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.

  • CVE-2023-25577

    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.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.

For Debian 10 buster, these problems have been fixed in version 0.14.1+dfsg1-4+deb10u2.

We recommend that you upgrade your python-werkzeug packages.

For the detailed security status of python-werkzeug please refer to its security tracker page at:

Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: