Inefficient Regular Expression Complexity Affecting rabbitmq-server package, versions <4.3.2-1


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.26% (16th percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-RABBITMQSERVER-20128097
  • published25 Sept 2026
  • disclosed23 Sept 2026

Introduced: 23 Sep 2026

NewCVE-2026-67240  (opens in a new tab)
CWE-1333  (opens in a new tab)

How to fix?

Upgrade Debian:unstable rabbitmq-server to version 4.3.2-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream rabbitmq-server package and not the rabbitmq-server package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

RabbitMQ is a messaging and streaming broker. Prior to versions 4.2.7 and 4.3.1, pattern_to_regex maps % -> .? and _ -> ., then compiles ^...$ with only [unicode]; re:run is called with only [{capture, none}] - no explicit match_limit. A pattern like %%..._%X becomes ^.?..?.....?.X$ with overlapping lazy quantifiers. The whole-expression cap is ?MAX_EXPRESSION_LENGTH=4096 chars / ?MAX_TOKENS=200; a LIKE string literal is one token, so ~2000 %_ pairs fit. SQL filters are accepted unconditionally at rabbit_amqp_session.erl:3264 (no feature flag). Evaluated per-message at rabbit_stream_queue.erl:1439. OTP's default 10M match_limit caps each match at ~100-200 ms (not seconds), and the re NIF yields to the scheduler. An authenticated AMQP 1.0 consumer with read+write on a stream queue can cause ~100-200 ms of CPU per delivered message via a crafted LIKE filter, multiplied across thousands of messages and parallel sessions - a substantial backtracking-driven CPU amplification. Preconditions include AMQP 1.0 with stream queues in use Attacker can attach a receiver with a filter (read permission) and publish messages with long property values (write permission). This issue is fixed in versions 4.2.7 and 4.3.1.

CVSS Base Scores

version 3.1