CVE-2026-27889 — Integer Overflow or Wraparound in Nats-io Nats-server V2

CWE-190 — Integer Overflow or WraparoundCWE-1286 — Improper Validation of Syntactic Correctness of Input8 documents6 sources
Severity
7.5HIGHNVD
EPSS
0.1%
top 76.06%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
4
Linuxfoundation Nats-serverGithub.com Nats-io Nats-server V2Debian Nats-server+1 more
Timeline
PublishedMar 25
Latest updateMar 26

Description

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and…

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitability: 3.9 | Impact: 3.6

Affected Packages5 packages

▶debiandebian/nats-server< nats-server 2.12.6-1 (forky)
▶NVDlinuxfoundation/nats-server2.2.0 — 2.11.14+1
▶Gogithub.com/nats-io_nats-server_v22.2.0 — 2.11.14+1
▶Debianlinuxfoundation/nats-server< 2.12.6-1
▶CVEListV5nats-io/nats-server>= 2.12.0, < 2.12.5, >= 2.2.0, < 2.11.14+1

🔴Vulnerability Details

4
OSV
NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead in github.com/nats-io/nats-server↗2026-03-26
▶
OSV
CVE-2026-27889: NATS-Server is a High-Performance server for NATS↗2026-03-25
▶
OSV
NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead↗2026-03-25
▶
GHSA
NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead↗2026-03-25
▶

📋Vendor Advisories

2
Red Hat
github.com/nats-io/nats-server: NATS-Server: Denial of Service via malformed WebSockets frame↗2026-03-25
▶
Debian
CVE-2026-27889: nats-server - NATS-Server is a High-Performance server for NATS.io, a cloud and edge native me...↗2026
▶

🕵️Threat Intelligence

1
Wiz
CVE-2026-27889 Impact, Exploitability, and Mitigation Steps | Wiz↗
▶