Allocation of Resources Without Limits or Throttling in nats-server - #VU166209
Published: November 13, 2026
Vulnerability identifier: #VU166209
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/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 attacker to cause a denial of service affecting the entire server process through resource exhaustion.
The vulnerability exists due to allocation of resources without consistently enforced size limits in the nats-server MQTT packet reader when processing subscription requests after CONNECT. A remote attacker can send oversized subscription packets that reach buffering and filter parsing despite max_payload to cause excessive memory allocations and exhaust server resources before subscription-count limits are applied.
Affected software
nats-server
Remediation
Install security update from vendor's website.
nats-server - addressed in versions 2.14.8, 2.15.1