Allocation of Resources Without Limits or Throttling in nats-server - #VU166204
Published: November 13, 2026
Vulnerability identifier: #VU166204
CSH Severity: Low
CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-770
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to exhaust storage available to their account and cause a denial of service for other MQTT users of that account.
The vulnerability exists due to allocation of persistent storage without adequate limits in the nats-server MQTT QoS 2 delivery-state handling when processing acknowledgements that do not correspond to an outstanding delivery. A remote user can send unexpected MQTT acknowledgements to accumulate unnecessary persistent records in JetStream and exhaust account storage, disrupting MQTT service.
Affected software
nats-server
Remediation
Install security update from vendor's website.
nats-server - update to 2.15.1