CVE-2026-27889

unknown

Published 2026-03-25 · Modified 2026-03-27

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CVSS v3

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CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v4 NEW

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not yet in upstream

VIR risk

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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.

Predictions

Exploit likelihood

30%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

OS impact

OS	Version	Status	Fixed in
sles		affected
debian	bookworm	affected
debian	forky	fixed	`2.12.6-1`
debian	sid	fixed	`2.12.6-1`
debian	trixie	affected

Package impact

Ecosystem	Package	Vulnerable	Fixed
Go	github.com/nats-io/nats-server/v2	`>=2.2.0,<2.11.14`	`2.11.14`
Go	github.com/nats-io/nats-server/v2	`>=2.12.0,<2.12.5`	`2.12.5`
Go	github.com/nats-io/nats-server

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.