# CVE-2026-55512: nebula-mesh: Unauthenticated OIDC login endpoint allocates unbounded in-memory state entries without rate limiting

> Unauthenticated attackers can exhaust memory in nebula-mesh by flooding the OIDC login endpoint, causing denial of service when OIDC is enabled.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Sep 2026
- **Updated:** 9 Sep 2026
- **Also known as:** GHSA-m3cx-mwpg-32jg, GO-2026-5989

## What is CVE-2026-55512?

CVE-2026-55512 is a medium-severity denial of service vulnerability in forgekeep nebula-mesh, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

nebula-mesh is a self-hosted control plane for Slack Nebula mesh VPN. From version 0.2.0 to before version 0.5.0, when OIDC is enabled, GET /ui/oidc/login is reachable without authentication and is registered outside the Web UI rate-limited auth routes. Every request creates a fresh random OIDC state value and stores it in an in-memory map for 10m. Expired states are swept lazily, but there is no rate limit or maximum live-state cap on the allocation path. An unauthenticated remote client can therefore grow OIDC.states for the full state TTL, bounded by request throughput rather than by configured auth rate limits. This issue has been patched in version 0.5.0.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-55512?

4 open source packages ship an affected version, including github.com/forgekeep/nebula-mesh and github.com/juev/nebula-mesh.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/forgekeep/nebula-mesh` | Go | From 0.2.0 | 0.5.0 |
| `github.com/forgekeep/nebula-mesh` | Go | From 0.2.0 | 0.5.0 |
| `github.com/forgekeep/nebula-mesh` | Go | From 0.4.0 | 0.5.0 |
| `github.com/juev/nebula-mesh` | Go | From 0.2.0 | None |

## How do I fix CVE-2026-55512?

Upgrade github.com/forgekeep/nebula-mesh to 0.5.0 or later.

## Is CVE-2026-55512 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55512 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55512 and fix it if it is affected.

What it is: CVE-2026-55512 is a medium-severity denial of service vulnerability in forgekeep nebula-mesh, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55512 exists.

Affected packages and fixed versions:
- github.com/forgekeep/nebula-mesh (Go): affected from 0.2.0; fixed in 0.5.0
- github.com/forgekeep/nebula-mesh (Go): affected from 0.2.0; fixed in 0.5.0
- github.com/forgekeep/nebula-mesh (Go): affected from 0.4.0; fixed in 0.5.0
- github.com/juev/nebula-mesh (Go): affected from 0.2.0; 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-2026-55512/ (Markdown: https://insights.sbomify.com/CVE-2026-55512/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55512
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55512
- OSV: https://osv.dev/vulnerability/CVE-2026-55512

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55512/
Summaries are generated and may contain mistakes; the official description above is the record.