CVE-2026-67234: RabbitMQ: Non-RFC-conformant cookie name when clearing the auth-mechanism preference

Description

RabbitMQ is a messaging and streaming broker. From 4.2.0 until 4.2.8 and 4.3.2, get_auth_mechanism/1 used term_to_binary/1 on the strict_auth_mechanism or preferred_auth_mechanism atom when clearing the corresponding cookie, producing a non-ASCII cookie name that violates RFC 6265 and can prevent the browser from deleting the preference. The issue is not directly exploitable for code execution or data exfiltration; its security relevance is limited to stale authentication-mechanism preferences persisting across logout and login cycles. This issue is fixed in versions 4.2.8 and 4.3.2.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Attack vector

Network

Complexity

Low

Privileges

None

User interaction

Required

Confidentiality

None

Integrity

Low

Availability

None

Scope

Unchanged

Exploitation

Is it being used?

Exploit prediction (EPSS)0.4% · higher than 37% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

RA

rabbitmq-server · rabbitmq

>= 4.2.0, < 4.2.8; >= 4.3.0, < 4.3.2 · source: vendor

RS

Rabbitmq Server · Broadcom

4.2.0 before 4.2.8; 4.3.0 before 4.3.2 · source: NVD