CVE-2026-27889: CWE-190: Integer Overflow or Wraparound in nats-io nats-server
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.
AI Analysis
Technical Summary
NATS-Server, a high-performance messaging system, contains an integer overflow or wraparound vulnerability (CWE-190) triggered by malformed WebSockets frames. This occurs before authentication due to a missing sanity check, allowing any unauthenticated user able to connect to the WebSockets port to cause a server panic and denial of service. The vulnerability affects versions >=2.2.0 and <2.11.14 and <2.12.5. Fixed in versions 2.11.14 and 2.12.5. The vulnerability requires the deployment to expose the WebSockets port to untrusted networks. Red Hat advisory confirms the impact and lack of currently effective mitigations meeting their criteria, recommending upgrading to fixed versions where possible.
Potential Impact
Successful exploitation results in a denial of service by causing the nats-server to panic and crash. There is no impact on confidentiality or integrity. The attack can be performed remotely without authentication and requires network access to the WebSockets port. The vulnerability affects availability of the service.
Mitigation Recommendations
A fix is available in nats-server versions 2.11.14 and 2.12.5. Users are strongly advised to upgrade to these or later versions to remediate the vulnerability. If upgrading is not immediately possible, mitigating exposure by restricting access to the WebSockets port from untrusted endpoints or disabling WebSockets usage can reduce risk. Red Hat notes that no mitigation currently meets their criteria for ease of use and applicability, so patching is the recommended approach.
CVE-2026-27889: CWE-190: Integer Overflow or Wraparound in nats-io nats-server
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.
CVSS v3.1
Score 7.5high
Affected software
nats-io
nats-server
pkg:github/nats-io/nats-serverRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
NATS-Server, a high-performance messaging system, contains an integer overflow or wraparound vulnerability (CWE-190) triggered by malformed WebSockets frames. This occurs before authentication due to a missing sanity check, allowing any unauthenticated user able to connect to the WebSockets port to cause a server panic and denial of service. The vulnerability affects versions >=2.2.0 and <2.11.14 and <2.12.5. Fixed in versions 2.11.14 and 2.12.5. The vulnerability requires the deployment to expose the WebSockets port to untrusted networks. Red Hat advisory confirms the impact and lack of currently effective mitigations meeting their criteria, recommending upgrading to fixed versions where possible.
Potential Impact
Successful exploitation results in a denial of service by causing the nats-server to panic and crash. There is no impact on confidentiality or integrity. The attack can be performed remotely without authentication and requires network access to the WebSockets port. The vulnerability affects availability of the service.
Mitigation Recommendations
A fix is available in nats-server versions 2.11.14 and 2.12.5. Users are strongly advised to upgrade to these or later versions to remediate the vulnerability. If upgrading is not immediately possible, mitigating exposure by restricting access to the WebSockets port from untrusted endpoints or disabling WebSockets usage can reduce risk. Red Hat notes that no mitigation currently meets their criteria for ease of use and applicability, so patching is the recommended approach.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-02-24T15:19:29.716Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2026-27889","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:22347","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:21769","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:23345","vendor":"Red Hat"}]
Threat ID: 69c43b99f4197a8e3b7c5650
Added to database: 03/25/2026, 19:46:33 UTC
Last enriched: 08/13/2026, 16:31:55 UTC
Last updated: 09/12/2026, 10:01:30 UTC
Views: 125
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