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CVE-2026-27889
7.5 HIGH
- CVSS version: 3.1
- Attack vector (AV): NETWORK
- Attack complexity (AC): LOW
- Privileges required (PR): NONE
- User interaction (UI): NONE
- Scope (S): UNCHANGED
- Confidentiality impact (C): NONE
- Integrity impact (I): NONE
- Availability impact (A): HIGH
NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
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.
References
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https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6 x_refsource_CONFIRM
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https://advisories.nats.io/CVE/secnote-2026-03.txt x_refsource_MISC
Affected products
nats-server
- ==>= 2.12.0, < 2.12.5
- ==>= 2.2.0, < 2.11.14
Package maintainers
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@derekcollison Derek Collison <derek@nats.io>
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@swdunlop Scott W. Dunlop <swdunlop@gmail.com>