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CVE-2023-23934

Wrkzeug's incorrect parsing of nameless cookies leads to __Host- cookies bypass

Description

Werkzeug is a comprehensive WSGI web application library. 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 prior to 2.2.3 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. The issue is fixed in Werkzeug 2.2.3.

Timeline

  1. ID reserved

    By GitHub_M

  2. · 26 days later

    Published

  3. · 2 years later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2023-23934, by who scored it
Scored byCVSSScoreVector
GitHub_MCNA (assigner)3.1Low2.6CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N
NVDNVD · Modified3.1Low3.5CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
EPSS (exploitation in 30 days)
0.51% · top 56% of all CVEs (11 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 2.6.

Affected products

Affected packages

From reviewed advisories of the GitHub Advisory Database.

References

References5

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

CVE-2023-23934 badge
[![CVE-2023-23934](https://cveledger.app/badge/CVE-2023-23934.svg)](https://cveledger.app/cve/CVE-2023-23934)

Record last updated .