Authenticated topic authorization bypass via regex injection
Published May 27, 2026 · Updated May 27, 2026
Authorization bypass in RabbitMQ Server 4.2.0 through 4.2.3 allows remote authenticated users to read and write restricted MQTT topics. The MQTT plugin substitutes the user-controlled client_id from the CONNECT packet into topic-permission regular expressions without escaping metacharacters. Exploitation requires a valid MQTT account and an administrator-defined topic permission that expands {client_id}; injected operators broaden subscriptions and publications beyond the account's intended topics.
Summary
What happened
Authorization bypass in RabbitMQ Server 4.2.0 through 4.2.3 allows remote authenticated users to read and write restricted MQTT topics. The MQTT plugin substitutes the user-controlled client_id from the CONNECT packet into topic-permission regular expressions without escaping metacharacters. Exploitation requires a valid MQTT account and an administrator-defined topic permission that expands {client_id}; injected operators broaden subscriptions and publications beyond the account's intended topics.
The record
- CVE
- CVE-2026-44838
- Published
- May 27, 2026
- Updated
- May 27, 2026
- Vendor
- RabbitMQ
- Product
- RabbitMQ Server
- Classifications
- CWE-863, T1565.002
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 27, 2026CVE publishedPublication date reported by the CVE source.
- May 27, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 4.2.0, < 4.2.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo