CVE-2026-33219

unknown

Published 2026-03-24 · 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:L

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. Prior to versions 2.11.15 and 2.12.6, a malicious client which can connect to the WebSockets port can cause unbounded memory use in the nats-server before authentication; this requires sending a corresponding amount of data. This is a milder variant of CVE-2026-27571. That earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable websockets if not required for project deployment.

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	`<2.11.15`	`2.11.15`
Go	github.com/nats-io/nats-server/v2	`>=2.12.0-RC.1,<2.12.6`	`2.12.6`
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.