What is CVE-2026-27889?

CVE-2026-27889 is a high-severity vulnerability in Nats-io Nats-server, classified under Integer Overflow or Wraparound. CVSS score: 7.5/10. Published 2026-03-25.

How severe is CVE-2026-27889?

High severity. CVSS v3 base score is 7.5 out of 10.

Integer overflow in Nats-io Nats-server

CVE-2026-27889

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 i…

Vulnerability class: Integer Overflow

EPSS: 0.001 (26.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Nats-io Nats-server — versions >= 2.2.0, < 2.11.14, >= 2.12.0, < 2.12.5

Weakness classification (CWE)

CWE-190 — Integer Overflow or Wraparound

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6 (x_refsource_CONFIRM)
https://advisories.nats.io/CVE/secnote-2026-03.txt (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-27889?: CVE-2026-27889 is a high-severity vulnerability in Nats-io Nats-server, classified under Integer Overflow or Wraparound. CVSS score: 7.5/10. Published 2026-03-25.
How severe is CVE-2026-27889?: High severity. CVSS v3 base score is 7.5 out of 10.