# CVE-2026-33246: NATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers > Attackers can spoof identity headers in NATS leafnode connections, bypassing client-side trust checks and potentially accessing unauthorized data. - **Severity:** Medium 6.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 25 Mar 2026 - **Updated:** 28 Mar 2026 - **Also known as:** BIT-nats-2026-33246, CLEANSTART-2026-DS19189, DEBIAN-CVE-2026-33246, ECHO-6731-3b07-4b9f, GHSA-55h8-8g96-x4hj, GO-2026-4830, JLSEC-2026-1130, MINI-3jwm-2wr6-97qc, MINI-4pgv-h6mp-q76g, MINI-c33v-236c-pphv, MINI-c74h-gjw9-895r, MINI-f5cg-93f2-3fh9, MINI-fr9m-mm65-jm34, MINI-p957-7vxv-9hqh, ROOT-APP-GOBINARY-CVE-2026-33246, UBUNTU-CVE-2026-33246 ## What is CVE-2026-33246? CVE-2026-33246 is a medium-severity authentication bypass vulnerability in nats-io nats-server, published on 25 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim. ### Official description NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server offers a `Nats-Request-Info:` message header, providing information about a request. This is supposed to provide enough information to allow for account/user identification, such that NATS clients could make their own decisions on how to trust a message, provided that they trust the nats-server as a broker. A leafnode connecting to a nats-server is not fully trusted unless the system account is bridged too. Thus identity claims should not have propagated unchecked. Prior to versions 2.11.15 and 2.12.6, NATS clients relying upon the Nats-Request-Info: header could be spoofed. This does not directly affect the nats-server itself, but the CVSS Confidentiality and Integrity scores are based upon what a hypothetical client might choose to do with this NATS header. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available. Weakness: CWE-290 (Authentication Bypass by Spoofing), CWE-287 (Improper Authentication) ## Which versions are affected by CVE-2026-33246? 9 open source packages ship an affected version, including github.com/nats-io/nats-server/v2, nats and github.com/nats-io/nats-server. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/nats-io/nats-server/v2` | Go | All versions | 2.11.15, 2.12.6 | | `github.com/nats-io/nats-server/v2` | Go | All versions | 2.11.15 | | `github.com/nats-io/nats-server/v2` | Go | All versions | 2.11.15 | | `github.com/nats-io/nats-server/v2` | Go | From 2.12.0-RC.1 | 2.12.6 | | `github.com/nats-io/nats-server/v2` | Go | From 2.12.0-RC.1 | 2.12.6 | | `nats` | Bitnami | All versions | 2.11.15, 2.12.6 | | `github.com/nats-io/nats-server` | Go | All versions | None | | `github.com/nats-io/nats-server` | Go | All versions | None | | `github.com/nats-io/nats-server` | Go | All versions | None | Products: Linuxfoundation Nats-Server. ## How do I fix CVE-2026-33246? Upgrade github.com/nats-io/nats-server/v2 to a fixed version for your release line: 2.11.15 or 2.12.6. ## Is CVE-2026-33246 being exploited? There is no known exploitation of CVE-2026-33246 in the wild and no public exploit code. ## Other vulnerabilities in nats-io nats-server - [CVE-2022-28357](https://insights.sbomify.com/CVE-2022-28357/): NATS nats-server allows directory traversal via unintended path to a management action (critical 9.8) - [CVE-2026-58253](https://insights.sbomify.com/CVE-2026-58253/): NATS Server: Route API Auth Bypass (high 8.8) - [CVE-2022-24450](https://insights.sbomify.com/CVE-2022-24450/): Incorrect Authorization in NATS nats-server (high 8.8) - [CVE-2026-33216](https://insights.sbomify.com/CVE-2026-33216/): NATS has MQTT plaintext password disclosure (high 8.6) - [CVE-2026-58207](https://insights.sbomify.com/CVE-2026-58207/): NATS Server: Remote crash via integer overflow in Connz pagination (high 7.7) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-33246 and fix it if it is affected. What it is: CVE-2026-33246 is a medium-severity authentication bypass vulnerability in nats-io nats-server, published on 25 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-33246 in the wild and no public exploit code. Affected packages and fixed versions: - github.com/nats-io/nats-server/v2 (Go): affected all versions; fixed in 2.11.15, 2.12.6 - github.com/nats-io/nats-server/v2 (Go): affected all versions; fixed in 2.11.15 - github.com/nats-io/nats-server/v2 (Go): affected all versions; fixed in 2.11.15 - github.com/nats-io/nats-server/v2 (Go): affected from 2.12.0-RC.1; fixed in 2.12.6 - github.com/nats-io/nats-server/v2 (Go): affected from 2.12.0-RC.1; fixed in 2.12.6 - nats (Bitnami): affected all versions; fixed in 2.11.15, 2.12.6 - github.com/nats-io/nats-server (Go): affected all versions; no fix listed - github.com/nats-io/nats-server (Go): affected all versions; no fix listed - github.com/nats-io/nats-server (Go): affected all versions; no fix listed Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-33246/ (Markdown: https://insights.sbomify.com/CVE-2026-33246/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33246 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33246 - OSV: https://osv.dev/vulnerability/CVE-2026-33246 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-33246/ Summaries are generated and may contain mistakes; the official description above is the record.