CVE-2026-27571
MEDIUM
GHSA-qrvq-68c2-7grw
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
3Description
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The WebSockets handling of NATS messages handles compressed messages via the WebSockets negotiated compression. Prior to versions 2.11.2 and 2.12.3, the implementation bound the memory size of a NATS message but did not independently bound the memory consumption of the memory stream when constructing a NATS message which might then fail validation for size reasons. An attacker can use a compression bomb to cause excessive memory consumption, often resulting in the operating system terminating the server process. The use of compression is negotiated before authentication, so this does not require valid NATS credentials to exploit. The fix, present in versions 2.11.2 and 2.12.3, was to bounds the decompression to fail once the message was too large, instead of continuing on. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points.
Analysis
NATS Server versions prior to 2.11.2 and 2.12.3 fail to properly limit memory allocation during WebSocket compression, allowing unauthenticated attackers to trigger denial of service through compression bomb attacks that exhaust server memory. The vulnerability is exploitable pre-authentication since compression negotiation occurs before credential validation. …
Sign in for full analysis, threat intelligence, and remediation guidance.
Remediation
Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Vendor patch is available.
Sign in for detailed remediation steps.
Priority Score
Vendor Status
Share
External POC / Exploit Code
Leaving vuln.today