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Fencer Vulns
high 8.1

CVE-2026-44838 json

RabbitMQ MQTT Topic Permission Authorization Bypass

published 2026-05-27 5 mo ago modified 2026-10-26 14 d ago also BIT-rabbitmq-2026-44838 , EUVD-2026-32548 , GHSA-x866-xp2g-cx8v

cvss
8.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 10%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami rabbitmq 4.2.4
  • broadcom rabbitmq_server 4.2.4
  • pivotal_software rabbitmq 4.2.4
  • vmware rabbitmq 4.2.4
  • rabbitmq-server4.3 hummingbird 1 4.3.4-0.1.hum1
  • rabbitmq-server4.2 hummingbird 1 4.2.9-0.1.hum1

red hat advisories RHSA-2026:45128RHSA-2026:42387

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-44838 updated cvss 8.1

rabbitmq-server: RabbitMQ: Authorization bypass via regular expression injection in MQTT client ID

  • Red Hat Hardened Images rabbitmq-server4.2 4.2.9-0.1.hum1, rabbitmq-server4.3 4.3.4-0.1.hum1
    fixed: vendor fix RHSA-2026:42387
  • Red Hat OpenStack Platform 16.2 rabbitmq-server Red Hat OpenStack Platform 17.1 rabbitmq-server Red Hat OpenStack Platform 18.0 rabbitmq-server
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
5 mo ago

Exploit prediction

0.20% chance of exploitation in the next 30 days, higher than 10% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 5.3 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
CNA 4.0 5.3 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
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
OSV 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
bitnami rabbitmq
>=4.2.0, <4.2.4
4.2.4

Affected products

  • rabbitmq rabbitmq-server

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.