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 which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.
CVE-2026-27889
HIGHPre-NVD 7.57.5
EchelonGraph scoreLOW confidence
This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: secondary
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5(low)
- EPSS
- 43.6%
- KEV
- Not listed
Published
March 25, 2026
Last Modified
June 30, 2026
Advisory Details (8)
Auto-updated Jul 3, 2026🔬 Proof of concept available. Patch available. Sources: github, redhat.
redhat Patch Available
redhat
2451447 – (CVE-2026-27889) CVE-2026-27889 github.com/nats-io/nats-server: NATS-Server: Denial of Service via malformed WebSockets frame
https://bugzilla.redhat.com/show_bug.cgi?id=2451447redhat Patch Available
redhat Patch Available
redhat Patch Available
github Patch Available🟡 PoC Available
Pre-auth remote server crash via WebSocket frame length overflow in wsRead · Advisory · nats-io/nats-server · GitHub
https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6Vendor Advisories for CVE-2026-27889(3)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:23345Red Hat Product SecurityHigh
Red Hat Security Advisory: Multicluster Global Hub 1.6.2 security update
- RHSA-2026:22347Red Hat Product SecurityHigh
Red Hat Security Advisory: Multicluster Global Hub 1.4.5 security update
- RHSA-2026:21769Red Hat Product SecurityHigh
Red Hat Security Advisory: Multicluster Global Hub 1.5.4 security update
Patch Availability(3)
| Vendor / Ecosystem | Fixed in / Patch | Released | Source |
|---|---|---|---|
| redhat | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1780167118 | 2026-06-04 | redhat |
| redhat | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1779579439 | 2026-06-01 | redhat |
| redhat | multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1778867753 | 2026-05-28 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(2 across 1 ecosystem)
Go(2)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| github.com/nats-io/nats-server | — | — | — |
| github.com/nats-io/nats-server/v2 | — | 2.11.14 | — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 11× in last 7d / 14× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 02:23 UTCEPSS rescore
- 2026-07-06 02:23 UTCEPSS rescore
- 2026-07-05 02:30 UTCEPSS rescore
- 2026-07-04 06:31 UTCEPSS rescore
- 2026-07-04 06:31 UTCEPSS rescore
- 2026-07-01 15:06 UTCEPSS rescore
- 2026-07-01 15:06 UTCEPSS rescore
- 2026-06-30 23:22 UTCEPSS rescore
- 2026-06-30 23:22 UTCEPSS rescore
- 2026-06-30 04:37 UTCEG score recompute
- 2026-06-30 04:37 UTCVendor advisory
- 2026-06-30 04:32 UTCNVD updatefirst tracked
Related CVEs(same vendor + same CWE)
Same vendor
10 shownredhat
Same CWE
10 shownCWE-190
- CVE-2009-0947EG 9.8CRITICAL
- CVE-2013-2729EG 9.8 KEVEPSS 99%CRITICAL
- CVE-2005-1141EG 9.8CRITICAL
- CVE-2005-0102EG 9.8CRITICAL
- CVE-2002-0391EG 9.8EPSS 99%CRITICAL
- CVE-2002-0639EG 9.8EPSS 97%CRITICAL
- CVE-2013-3486EG 9.6CRITICAL
- CVE-2013-2596NVD 7.8EG 9.0 KEVHIGH
- CVE-2012-5054NVD 8.8EG 9.0 KEVEPSS 97%HIGH
- CVE-2011-1823NVD 7.8EG 9.0 KEVEPSS 99%HIGH
Frequently asked(5)
What is CVE-2026-27889?
CVE-2026-27889 is a high vulnerability published on March 25, 2026. 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…
When was CVE-2026-27889 disclosed?
CVE-2026-27889 was first published in the National Vulnerability Database on March 25, 2026, with the most recent update on June 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-27889 actively exploited?
CVE-2026-27889 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 43.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-27889?
CVE-2026-27889 has a CVSS v3 base score of 7.5 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-27889?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-27889, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-27889
Is Your Infrastructure Affected by CVE-2026-27889?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.