RabbitMQ: Consistent-hash exchange unbounded weight

Summary

RabbitMQ is a messaging and streaming broker. Prior to versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0, add_binding/3 parses the routing key as an integer weight N and computes ring positions with lists:seq(NextN0, NextN0 + N - 1). validate_binding/2 only checks N >= 1 , no upper bound. The resulting list is stored in the exchange's Khepri record, replicated cluster-wide, and reloaded on restart. A user with write permission on a consistent-hash exchange and read on a queue can create a binding whose routing key (the hash-ring weight) is an arbitrarily large integer. The broker allocates a list of that many integers via lists:seq/2 and persists it to Khepri across all cluster nodes , a single binding with weight 100000000 allocates ~800 MB on every node and survives restarts. Preconditions include rabbitmq_consistent_hash_exchange plugin enabled write permission on a consistent-hash exchange + read on a queue (standard binding perms). This issue is fixed in versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0.

Timeline

1. Sep 23, 2026, 8:38 PM UTCCVE published
2. Sep 24, 2026, 2:19 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Sep 24, 2026, 2:20 PM UTCRecord last updated

Affected versions

• rabbitmq rabbitmq-server

  From 3.13.0 · fixed in 3.13.15; From 4.0.0 · fixed in 4.0.20; From 4.1.0 · fixed in 4.1.11; From 4.2.0 · fixed in 4.2.6

• rabbitmqBitnami

  From 3.13.0 · fixed in 3.13.15; From 4.0.0 · fixed in 4.0.20; From 4.1.0 · fixed in 4.1.11; From 4.2.0 · fixed in 4.2.6

References 3