MQTT topic authorization bypass via unescaped hyphen
Published Sep 25, 2026 · Updated Sep 25, 2026
Regex escaping errors in RabbitMQ Server 4.x allow remote authenticated users to bypass MQTT topic permissions with a crafted client ID. escape_regex_char/1 omits the hyphen, so a client ID such as a-z expands inside a bracketed topic template into a regex range rather than a literal value. Exploitation requires low-privileged MQTT credentials and a topic permission template containing {client_id} inside a character class; successful bypass permits unauthorized topic reads and writes in the affected ranges 4.0.0 through 4.0.22, 4.1.0 through 4.1.13, 4.2.0 through 4.2.8, and 4.3.2.
Summary
What happened
Regex escaping errors in RabbitMQ Server 4.x allow remote authenticated users to bypass MQTT topic permissions with a crafted client ID. escape_regex_char/1 omits the hyphen, so a client ID such as a-z expands inside a bracketed topic template into a regex range rather than a literal value. Exploitation requires low-privileged MQTT credentials and a topic permission template containing {client_id} inside a character class; successful bypass permits unauthorized topic reads and writes in the affected ranges 4.0.0 through 4.0.22, 4.1.0 through 4.1.13, 4.2.0 through 4.2.8, and 4.3.2.
The record
- CVE
- CVE-2026-67407
- Published
- Sep 25, 2026
- Updated
- Sep 25, 2026
- Vendor
- RabbitMQ
- Product
- RabbitMQ Server
- Classifications
- T1210
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 25, 2026CVE publishedPublication date reported by the CVE source.
- Sep 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 4.0.0, < 4.0.23
- Affected versionversion=>= 4.1.0, < 4.1.14
- Affected versionversion=>= 4.2.0, < 4.2.9
- Affected versionversion=>= 4.3.2, < 4.3.3
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.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
- MQTT client-ID regex-range permission-bypass reproductionfunctional · demonstrated
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Technologies
Your stack
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Your stack
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