CVE-2026-44838
RabbitMQ MQTT Topic Permission Authorization Bypass
RabbitMQ is a messaging and streaming broker. From 4.2.0 to before 4.2.4, RabbitMQ's MQTT plugin allows for topic-level authorization using regular expressions with variable substitution. Administrators can create patterns such as ^{client_id}-sensors$ to restrict user access to topics that include their client ID. However, the client_id is provided by the user in the MQTT CONNECT packet and is inserted into the regex pattern without escaping special regex characters. This flaw enables an authenticated MQTT user to inject regex operators to bypass authorization. This vulnerability is fixed in 4.2.4 and 4.3.0.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
5.3
RabbitMQ MQTT Topic Permission Authorization Bypass
RabbitMQ is a messaging and streaming broker. From 4.2.0 to before 4.2.4, RabbitMQ's MQTT plugin allows for topic-level authorization using regular expressions with variable substitution. Administrators can create patterns such as ^{client_id}-sensors$ to restrict user access to topics that include their client ID. However, the client_id is provided by the user in the MQTT CONNECT packet and is inserted into the regex pattern without escaping special regex characters. This flaw enables an authenticated MQTT user to inject regex operators to bypass authorization. This vulnerability is fixed in 4.2.4 and 4.3.0.
- Record
CVE-2026-44838- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:H/SI:H/SA:N - Weakness
- CWE-863
- Updated
- 2026-11-02
EUVDEUVD-2026-32548
5.3
RabbitMQ is a messaging and streaming broker. From 4.2.0 to before 4.2.4, RabbitMQ's MQTT plugin allows for topic-level authorization using regular expressions with variable substitution. Administrators can create patterns such as ^{client_id}-sensors$ to restrict user access to topics that include their client ID. However, the client_id is provided by the user in the MQTT CONNECT packet and is inserted into the regex pattern without escaping special regex characters. This flaw enables an authenticated MQTT user to inject regex operators to bypass authorization. This vulnerability is fixed in 4.2.4 and 4.3.0.
- Record
EUVD-2026-32548- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:H/SI:H/SA:N - Updated
- 2026-11-02
NVD
5.3
RabbitMQ is a messaging and streaming broker. From 4.2.0 to before 4.2.4, RabbitMQ's MQTT plugin allows for topic-level authorization using regular expressions with variable substitution. Administrators can create patterns such as ^{client_id}-sensors$ to restrict user access to topics that include their client ID. However, the client_id is provided by the user in the MQTT CONNECT packet and is inserted into the regex pattern without escaping special regex characters. This flaw enables an authenticated MQTT user to inject regex operators to bypass authorization. This vulnerability is fixed in 4.2.4 and 4.3.0.
- Record
CVE-2026-44838- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N - Weakness
- CWE-863
- Updated
- 2026-11-02
OSV
5.3
RabbitMQ MQTT Topic Permission Authorization Bypass
RabbitMQ is a messaging and streaming broker. From 4.2.0 to before 4.2.4, RabbitMQ's MQTT plugin allows for topic-level authorization using regular expressions with variable substitution. Administrators can create patterns such as ^{client_id}-sensors$ to restrict user access to topics that include their client ID. However, the client_id is provided by the user in the MQTT CONNECT packet and is inserted into the regex pattern without escaping special regex characters. This flaw enables an authenticated MQTT user to inject regex operators to bypass authorization. This vulnerability is fixed in 4.2.4 and 4.3.0.
- Record
CVE-2026-44838- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:H/SI:H/SA:N - Weakness
- CWE-863
- Updated
- 2026-11-02
OSVRHSA-2026:42387
8.1
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
- Record
RHSA-2026:42387- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
OSVRHSA-2026:45128
8.1
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
- Record
RHSA-2026:45128- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-44838
5.3
RabbitMQ is a messaging and streaming broker. From 4.2.0 to before 4.2.4, RabbitMQ's MQTT plugin allows for topic-level authorization using regular expressions with variable substitution. Administrators can create patterns such as ^{client_id}-sensors$ to restrict user access to topics that include their client ID. However, the client_id is provided by the user in the MQTT CONNECT packet and is inserted into the regex pattern without escaping special regex characters. This flaw enables an authenticated MQTT user to inject regex operators to bypass authorization. This vulnerability is fixed in 4.2.4 and 4.3.0.
- Record
UBUNTU-CVE-2026-44838- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:H/SI:H/SA:N - Updated
- 2026-11-02
OSVBIT-rabbitmq-2026-44838 No score
RabbitMQ MQTT Topic Permission Authorization Bypass
RabbitMQ is a messaging and streaming broker. From 4.2.0 to before 4.2.4, RabbitMQ's MQTT plugin allows for topic-level authorization using regular expressions with variable substitution. Administrators can create patterns such as ^{client_id}-sensors$ to restrict user access to topics that include their client ID. However, the client_id is provided by the user in the MQTT CONNECT packet and is inserted into the regex pattern without escaping special regex characters. This flaw enables an authenticated MQTT user to inject regex operators to bypass authorization. This vulnerability is fixed in 4.2.4 and 4.3.0.
- Record
BIT-rabbitmq-2026-44838- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
rabbitmqBitnami |
4.2.0 up to 4.2.4 | 4.2.4 |
rabbitmq-server4.2Red Hat:hummingbird:1 |
before 0:4.2.9-0.1.hum1 | 0:4.2.9-0.1.hum1 |
rabbitmq-server4.3Red Hat:hummingbird:1 |
before 0:4.3.4-0.1.hum1 | 0:4.3.4-0.1.hum1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected | ||
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-44838 is a medium vulnerability (CVSS 5.3) in Broadcom Rabbitmq Server, published May 27, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.20%, the 10th percentile. Fixed in rabbitmq 4.2.4.
References
github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-x866-xp2g-cx8v
nvd.nist.gov/vuln/detail/CVE-2026-44838
github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44838.json
access.redhat.com/errata/RHSA-2026:42387
images.redhat.com
access.redhat.com/security/cve/CVE-2026-44838
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access.redhat.com/security/updates/classification
security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_42387.json
bugzilla.redhat.com/show_bug.cgi?id=2482208
cve.org/CVERecord?id=CVE-2026-44838
access.redhat.com/errata/RHSA-2026:45128
security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_45128.json
ubuntu.com/security/CVE-2026-44838