# CVE-2026-53602: nebula-mesh - Host revocation is not durable: blocked/offboarded hosts can regain a valid certificate

> Blocked or offboarded hosts can regain valid certificates because the control plane fails to enforce revocation and operator status during certificate issuance.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **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:** 4 Sep 2026
- **Also known as:** GHSA-339v-266x-79xr, GO-2026-5950

## What is CVE-2026-53602?

CVE-2026-53602 is a medium-severity missing authorization 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. Prior to version 0.3.7, two related authorization gaps let a host that should no longer be trusted obtain a fresh, valid Nebula certificate, because nebula-mgmt does not re-evaluate revocation/authorization state at certificate issuance time — only at poll time. Firstly, the blocklist is not enforced at sign / re-enroll time. internal/api/enroll.go:128 calls caMgr.Sign(...) without consulting the blocklist. The blocklist is only checked in the poll path (internal/api/updates.go:57, fingerprintInBlocklist). The blocklist is keyed by certificate fingerprint (internal/store/sqlite.go), so a re-enrollment produces a new fingerprint that is not in the blocklist. Secondly, renewal does not re-validate operator / CA status. Auto-renewal at poll time (internal/api/updates.go:285-319, signHostCert) reads host.Name, host.Groups, host.NebulaIPs from the DB and re-signs without checking whether the owning operator is still active or the CA still valid. DisableOperator (internal/store/sqlite_operators.go) revokes sessions and API keys but does not retire the operator's CAs, and pki/signer.go checks only CA cert time-expiry, not operator/CA status. This issue has been patched in version 0.3.7.

Weakness: CWE-862 (Missing Authorization), CWE-285 (Improper Authorization)

## Which versions are affected by CVE-2026-53602?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/forgekeep/nebula-mesh` | Go | All versions | 0.3.7 |
| `github.com/forgekeep/nebula-mesh` | Go | All versions | 0.3.7 |
| `github.com/forgekeep/nebula-mesh` | Go | All versions | 0.3.7 |

## How do I fix CVE-2026-53602?

Upgrade github.com/forgekeep/nebula-mesh to 0.3.7 or later.

## Is CVE-2026-53602 being exploited?

There is no known exploitation of CVE-2026-53602 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53602 and fix it if it is affected.

What it is: CVE-2026-53602 is a medium-severity missing authorization 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: There is no known exploitation of CVE-2026-53602 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/forgekeep/nebula-mesh (Go): affected all versions; fixed in 0.3.7
- github.com/forgekeep/nebula-mesh (Go): affected all versions; fixed in 0.3.7
- github.com/forgekeep/nebula-mesh (Go): affected all versions; fixed in 0.3.7

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-2026-53602/ (Markdown: https://insights.sbomify.com/CVE-2026-53602/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53602
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53602
- OSV: https://osv.dev/vulnerability/CVE-2026-53602

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53602/
Summaries are generated and may contain mistakes; the official description above is the record.