Vulnerability Details 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 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 25.2%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-27889
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cpe:2.3:a:linuxfoundation:nats-server:2.10.0
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cpe:2.3:a:linuxfoundation:nats-server:2.10.1
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cpe:2.3:a:linuxfoundation:nats-server:2.10.10
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cpe:2.3:a:linuxfoundation:nats-server:2.10.11
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cpe:2.3:a:linuxfoundation:nats-server:2.10.12
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cpe:2.3:a:linuxfoundation:nats-server:2.10.14
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cpe:2.3:a:linuxfoundation:nats-server:2.10.16
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cpe:2.3:a:linuxfoundation:nats-server:2.10.17
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cpe:2.3:a:linuxfoundation:nats-server:2.10.18
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cpe:2.3:a:linuxfoundation:nats-server:2.10.19
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cpe:2.3:a:linuxfoundation:nats-server:2.10.2
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cpe:2.3:a:linuxfoundation:nats-server:2.10.20
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cpe:2.3:a:linuxfoundation:nats-server:2.10.21
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cpe:2.3:a:linuxfoundation:nats-server:2.10.22
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cpe:2.3:a:linuxfoundation:nats-server:2.10.23
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cpe:2.3:a:linuxfoundation:nats-server:2.10.24
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cpe:2.3:a:linuxfoundation:nats-server:2.10.25
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cpe:2.3:a:linuxfoundation:nats-server:2.10.26
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cpe:2.3:a:linuxfoundation:nats-server:2.10.27
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cpe:2.3:a:linuxfoundation:nats-server:2.10.28
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cpe:2.3:a:linuxfoundation:nats-server:2.10.29
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cpe:2.3:a:linuxfoundation:nats-server:2.10.3
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cpe:2.3:a:linuxfoundation:nats-server:2.10.4
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cpe:2.3:a:linuxfoundation:nats-server:2.10.5
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cpe:2.3:a:linuxfoundation:nats-server:2.10.6
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cpe:2.3:a:linuxfoundation:nats-server:2.10.7
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cpe:2.3:a:linuxfoundation:nats-server:2.10.8
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cpe:2.3:a:linuxfoundation:nats-server:2.10.9
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cpe:2.3:a:linuxfoundation:nats-server:2.11.0
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cpe:2.3:a:linuxfoundation:nats-server:2.11.1
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cpe:2.3:a:linuxfoundation:nats-server:2.11.10
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cpe:2.3:a:linuxfoundation:nats-server:2.11.11
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cpe:2.3:a:linuxfoundation:nats-server:2.11.12
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cpe:2.3:a:linuxfoundation:nats-server:2.11.2
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cpe:2.3:a:linuxfoundation:nats-server:2.11.3
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cpe:2.3:a:linuxfoundation:nats-server:2.11.4
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cpe:2.3:a:linuxfoundation:nats-server:2.11.5
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cpe:2.3:a:linuxfoundation:nats-server:2.11.6
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cpe:2.3:a:linuxfoundation:nats-server:2.11.7
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cpe:2.3:a:linuxfoundation:nats-server:2.11.8
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cpe:2.3:a:linuxfoundation:nats-server:2.11.9
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cpe:2.3:a:linuxfoundation:nats-server:2.12.0
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cpe:2.3:a:linuxfoundation:nats-server:2.12.1
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cpe:2.3:a:linuxfoundation:nats-server:2.12.2
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cpe:2.3:a:linuxfoundation:nats-server:2.12.3
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cpe:2.3:a:linuxfoundation:nats-server:2.12.4
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cpe:2.3:a:linuxfoundation:nats-server:2.2.0
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cpe:2.3:a:linuxfoundation:nats-server:2.2.1
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cpe:2.3:a:linuxfoundation:nats-server:2.2.2
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cpe:2.3:a:linuxfoundation:nats-server:2.2.3
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cpe:2.3:a:linuxfoundation:nats-server:2.2.4
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cpe:2.3:a:linuxfoundation:nats-server:2.2.5
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cpe:2.3:a:linuxfoundation:nats-server:2.2.6
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cpe:2.3:a:linuxfoundation:nats-server:2.3.0
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cpe:2.3:a:linuxfoundation:nats-server:2.3.1
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cpe:2.3:a:linuxfoundation:nats-server:2.3.2
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cpe:2.3:a:linuxfoundation:nats-server:2.3.3
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cpe:2.3:a:linuxfoundation:nats-server:2.3.4
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cpe:2.3:a:linuxfoundation:nats-server:2.4.0
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cpe:2.3:a:linuxfoundation:nats-server:2.5.0
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cpe:2.3:a:linuxfoundation:nats-server:2.6.0
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cpe:2.3:a:linuxfoundation:nats-server:2.6.1
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cpe:2.3:a:linuxfoundation:nats-server:2.6.2
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cpe:2.3:a:linuxfoundation:nats-server:2.6.3
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cpe:2.3:a:linuxfoundation:nats-server:2.6.4
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cpe:2.3:a:linuxfoundation:nats-server:2.6.5
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cpe:2.3:a:linuxfoundation:nats-server:2.6.6
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cpe:2.3:a:linuxfoundation:nats-server:2.7.0
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cpe:2.3:a:linuxfoundation:nats-server:2.7.1
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cpe:2.3:a:linuxfoundation:nats-server:2.7.2
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cpe:2.3:a:linuxfoundation:nats-server:2.7.3
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cpe:2.3:a:linuxfoundation:nats-server:2.7.4
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cpe:2.3:a:linuxfoundation:nats-server:2.8.0
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cpe:2.3:a:linuxfoundation:nats-server:2.8.1
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cpe:2.3:a:linuxfoundation:nats-server:2.8.2
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cpe:2.3:a:linuxfoundation:nats-server:2.8.3
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cpe:2.3:a:linuxfoundation:nats-server:2.8.4
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cpe:2.3:a:linuxfoundation:nats-server:2.9.0
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cpe:2.3:a:linuxfoundation:nats-server:2.9.1
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cpe:2.3:a:linuxfoundation:nats-server:2.9.10
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cpe:2.3:a:linuxfoundation:nats-server:2.9.11
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cpe:2.3:a:linuxfoundation:nats-server:2.9.12
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cpe:2.3:a:linuxfoundation:nats-server:2.9.14
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cpe:2.3:a:linuxfoundation:nats-server:2.9.15
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cpe:2.3:a:linuxfoundation:nats-server:2.9.16
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cpe:2.3:a:linuxfoundation:nats-server:2.9.17
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cpe:2.3:a:linuxfoundation:nats-server:2.9.18
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cpe:2.3:a:linuxfoundation:nats-server:2.9.19
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cpe:2.3:a:linuxfoundation:nats-server:2.9.2
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cpe:2.3:a:linuxfoundation:nats-server:2.9.20
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cpe:2.3:a:linuxfoundation:nats-server:2.9.21
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cpe:2.3:a:linuxfoundation:nats-server:2.9.22
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cpe:2.3:a:linuxfoundation:nats-server:2.9.23
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cpe:2.3:a:linuxfoundation:nats-server:2.9.3
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cpe:2.3:a:linuxfoundation:nats-server:2.9.4
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cpe:2.3:a:linuxfoundation:nats-server:2.9.5
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cpe:2.3:a:linuxfoundation:nats-server:2.9.6
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cpe:2.3:a:linuxfoundation:nats-server:2.9.7
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cpe:2.3:a:linuxfoundation:nats-server:2.9.8
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cpe:2.3:a:linuxfoundation:nats-server:2.9.9