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Incorrect parsing of nameless cookies leads to __Host- cookies bypass

Low severity GitHub Reviewed Published Feb 14, 2023 in pallets/werkzeug • Updated Nov 19, 2024

Package

pip Werkzeug (pip)

Affected versions

< 2.2.3

Patched versions

2.2.3

Description

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.

References

@davidism davidism published to pallets/werkzeug Feb 14, 2023
Published by the National Vulnerability Database Feb 14, 2023
Published to the GitHub Advisory Database Feb 15, 2023
Reviewed Feb 15, 2023
Last updated Nov 19, 2024

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Adjacent
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N

EPSS score

0.064%
(30th percentile)

Weaknesses

CVE ID

CVE-2023-23934

GHSA ID

GHSA-px8h-6qxv-m22q

Source code

Credits

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