VulnerabilityModified

CVE-2023-23934

Browsers may allow "nameless" cookies that look like `=value` instead of `key=value`.

LOW 3.5EPSS 0.51%

Does this matter?

Lower severity and a low EPSS score (0.51%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 3.1: 3.5 LOWCVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
EPSS: 0.51% probability · 43th percentile
Public exploits: None in Exploit-DB
CISA KEV: Not listed
Weakness: CWE-20
Affected: palletsprojects/werkzeug
Source: security-advisories@github.com

EPSS trend

EPSS 0.5% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.