CVE-2026-66070: RabbitMQ: CORS * reflects Origin with Allow-Credentials

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-23 · updated 2026-10-19
Weakness: CWE-942

Description

RabbitMQ is a messaging and streaming broker. Prior to versions 3.13.17, 4.0.22, 4.1.13, and 4.2.6, match_origin/1 returned the bare reflected Origin and allowed credentials even when the wildcard "" was configured, so the response echoed the attacker's origin together with Access-Control-Allow-Credentials. The affected code is rabbit_mgmt_cors.erl. When the management plugin is configured with a wildcard CORS origin (cors_allow_origins = ""), the handler reflects the request Origin back in Access-Control-Allow-Origin and also sends Access-Control-Allow-Credentials: true. A malicious web page that a signed-in administrator visits can then use that administrator's cached HTTP Basic credentials to issue authenticated, state-changing requests to the management API. Preconditions include The management plugin is configured with the wildcard cors_allow_origins = "*", which is an explicit operator misconfiguration A target administrator has a cached HTTP Basic-auth session in the browser. This issue is fixed in versions 3.13.17, 4.0.22, 4.1.13, and 4.2.6.

Affected products

rabbitmq-server: from 3.13.0 before 3.13.17; from 4.0.0 before 4.0.22; from 4.1.0 before 4.1.13; from 4.2.0 before 4.2.6 — fixed in 3.13.17, 4.0.22, 4.1.13, 4.2.6

How to fix

Upgrade to a fixed version: rabbitmq-server 3.13.17, 4.0.22, 4.1.13, 4.2.6. Check the vendor advisory for mitigations.

References

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