CVE-2026-27889
NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
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 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.
INFO
Published Date :
March 25, 2026, 8:16 p.m.
Last Modified :
June 30, 2026, 3:17 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c |
Solution
- Update NATS-Server to version 2.11.14 or later.
- Update NATS-Server to version 2.12.5 or later.
- Restrict access to the WebSockets port.
- Ensure the network port is not exposed to untrusted endpoints.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-27889.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-27889 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-27889
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-27889 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-27889 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Jun. 30, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:/a:redhat:multicluster_globalhub:1.4::el9'], 'vendor': 'Red Hat', 'product': 'Multicluster Global Hub 1.4.5', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:multicluster_globalhub:1.5::el9'], 'vendor': 'Red Hat', 'product': 'Multicluster Global Hub 1.5.4', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:multicluster_globalhub:1.6::el9'], 'vendor': 'Red Hat', 'product': 'Multicluster Global Hub 1.6.2', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'defaultStatus': 'unaffected'}] Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-1286 Added Reference https://access.redhat.com/errata/RHSA-2026:21769 Added Reference https://access.redhat.com/errata/RHSA-2026:22347 Added Reference https://access.redhat.com/errata/RHSA-2026:23345 Added Reference https://access.redhat.com/security/cve/CVE-2026-27889 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2451447 Added Reference https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27889.json -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'nats-io', 'product': 'nats-server', 'versions': [{'status': 'affected', 'version': '>= 2.2.0, < 2.11.14'}, {'status': 'affected', 'version': '>= 2.12.0, < 2.12.5'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-27889', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-03-25T20:06:22.827675Z'} -
Initial Analysis by [email protected]
Mar. 26, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:* versions from (including) 2.12.0 up to (excluding) 2.12.5 *cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:* versions from (including) 2.2.0 up to (excluding) 2.11.14 Added Reference Type GitHub, Inc.: https://advisories.nats.io/CVE/secnote-2026-03.txt Types: Mitigation, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6 Types: Mitigation, Vendor Advisory -
New CVE Received by [email protected]
Mar. 25, 2026
Action Type Old Value New Value Added 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 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-190 Added Reference https://advisories.nats.io/CVE/secnote-2026-03.txt Added Reference https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6