{"id":"CVE-2023-23934","aliases":["GHSA-px8h-6qxv-m22q","PYSEC-2023-57"],"title":"Incorrect parsing of nameless cookies leads to __Host- cookies bypass","summary":"Incorrect parsing of nameless cookies leads to __Host- cookies bypass","severity":"low","cvss":2.6,"cvssVector":"CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N","vendor":"werkzeug","product":"werkzeug","ecosystem":"pip","affected":["werkzeug < 2.2.3"],"patched":["werkzeug 2.2.3"],"published":"2023-02-15","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:50:07.890803222Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-px8h-6qxv-m22q","references":[{"url":"https://github.com/pallets/werkzeug/security/advisories/GHSA-px8h-6qxv-m22q"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-23934"},{"url":"https://github.com/pallets/werkzeug/commit/cf275f42acad1b5950c50ffe8ef58fe62cdce028"},{"url":"https://github.com/pallets/werkzeug"},{"url":"https://github.com/pallets/werkzeug/releases/tag/2.2.3"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/werkzeug/PYSEC-2023-57.yaml"},{"url":"https://security.netapp.com/advisory/ntap-20230818-0003"},{"url":"https://www.debian.org/security/2023/dsa-5470"}],"tags":["osv","pip"],"epss":0.00507,"epssPercentile":0.42131,"ingestedAt":"2026-09-12T03:13:01.719Z","slug":"CVE-2023-23934","body":"## Overview\n\nBrowsers 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.\n\nWerkzeug <= 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.\n\n## Affected packages\n\n- `werkzeug < 2.2.3`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `werkzeug 2.2.3`","depth":"sunlit","depthScore":14,"depthScoreParts":{"impact":14.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}