# CVE-2026-41164: nuts-node: JWT type confusion in v1 access token introspection allows VP replay as access token

> Attackers can replay Verifiable Presentation JWTs as valid access tokens due to missing type validation, bypassing authentication controls.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 May 2026
- **Updated:** 27 May 2026
- **Also known as:** GHSA-9hmg-827w-9rhj, GO-2026-5291

## What is CVE-2026-41164?

CVE-2026-41164 is a medium-severity authentication bypass vulnerability in nuts-foundation nuts-node, published on 26 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

nuts-node is the reference implementation of the Nuts specification. Prior to 6.2.3 and 5.4.31, the v1 access token introspection endpoint (/auth/v1/introspect_access_token) accepts any JWT signed by a key present on the node, without validating the JWT type, issuer-to-key binding, or required claims. This allows a Verifiable Presentation (VP) JWT to be replayed as an access token and receive an active: true introspection response. This vulnerability is fixed in 6.2.3 and 5.4.31.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2026-41164?

3 open source packages ship an affected version, including github.com/nuts-foundation/nuts-node.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/nuts-foundation/nuts-node` | Go | All versions | None |
| `github.com/nuts-foundation/nuts-node` | Go | All versions to 1.1.0 | None |
| `github.com/nuts-foundation/nuts-node` | Go | All versions to 1.1.0 | None |

## How do I fix CVE-2026-41164?

Upgrade to a fixed version.

## Is CVE-2026-41164 being exploited?

There is no known exploitation of CVE-2026-41164 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-41164 and fix it if it is affected.

What it is: CVE-2026-41164 is a medium-severity authentication bypass vulnerability in nuts-foundation nuts-node, published on 26 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-41164 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/nuts-foundation/nuts-node (Go): affected all versions; no fix listed
- github.com/nuts-foundation/nuts-node (Go): affected all versions up to 1.1.0; no fix listed
- github.com/nuts-foundation/nuts-node (Go): affected all versions up to 1.1.0; 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-2026-41164/ (Markdown: https://insights.sbomify.com/CVE-2026-41164/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-41164
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-41164
- OSV: https://osv.dev/vulnerability/CVE-2026-41164

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-41164/
Summaries are generated and may contain mistakes; the official description above is the record.