# GHSA-6vgg-xhvh-38ff: nebula-mesh: POST /api/v1/hosts/{id}/mobile-bundle response lacks Cache-Control: no-store

> Missing cache-control headers on a mobile bundle API endpoint allow intermediaries to cache and leak freshly generated X25519 private keys.

- **Severity:** Not scored
- **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:** 12 Jun 2026
- **Also known as:** GO-2026-5191

## What is GHSA-6vgg-xhvh-38ff?

GHSA-6vgg-xhvh-38ff is a vulnerability in github.com/juev/nebula-mesh, published on 12 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

`internal/api/mobile_bundle.go:62-66` sets only `Content-Type: application/yaml`. The Web-UI sibling at `internal/web/handlers.go:1316-1321` sets `Cache-Control: no-store`, `Pragma: no-cache`, `Expires: 0`, `X-Content-Type-Options: nosniff` — and has a test asserting it. The API path was missed.

## Affected
All released versions up to v0.3.0.

## Threat model
The endpoint returns a freshly minted X25519 private key inline. Without `no-store`, any intermediary proxy or CDN that caches `200 OK` YAML responses retains the private key for its cache TTL. Same applies to browser disk cache for direct API hits. Combined with the cross-tenant authz advisory (critical), even a corrected authz layer would still leak via cache after fix.

## Suggested fix
Copy the four headers from the Web sibling:

```go
w.Header().Set("Content-Type", "application/yaml; charset=utf-8")
w.Header().Set("Cache-Control", "no-store")
w.Header().Set("Pragma", "no-cache")
w.Header().Set("Expires", "0")
w.Header().Set("X-Content-Type-Options", "nosniff")
```

Mirrors `internal/web/handlers.go:1316-1321`. Add a parallel test to the existing web-side coverage.

## Suggested patch

Verified locally: `go vet`, `go test -race -count=1 ./...`, `golangci-lint v2.12` all clean.

```diff
diff --git a/internal/api/mobile_bundle.go b/internal/api/mobile_bundle.go
index fc09da0..73152eb 100644
--- a/internal/api/mobile_bundle.go
+++ b/internal/api/mobile_bundle.go
@@ -58,8 +58,15 @@ func (s *Server) handleMobileBundle(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Return YAML bundle with proper content-type
+	// Return YAML bundle with proper content-type. The bundle inlines a
+	// freshly-minted X25519 private key, so suppress every layer of cache
+	// between server and operator (intermediate proxies/CDNs, browser disk
+	// cache). Mirrors the Web-UI sibling at internal/web/handlers.go.
 	w.Header().Set("Content-Type", "application/yaml; charset=utf-8")
+	w.Header().Set("Cache-Control", "no-store")
+	w.Header().Set("Pragma", "no-cache")
+	w.Header().Set("Expires", "0")
+	w.Header().Set("X-Content-Type-Options", "nosniff")
 	w.WriteHeader(http.StatusOK)
 	if _, err := w.Write(bundle); err != nil {
 		s.logger.Error("write mobile bundle response", "error", err)
diff --git a/internal/api/mobile_bundle_test.go b/internal/api/mobile_bundle_test.go
index dcb8cd9..da08b01 100644
--- a/internal/api/mobile_bundle_test.go
+++ b/internal/api/mobile_bundle_test.go
@@ -52,6 +52,19 @@ func TestHandleMobileBundle_Success(t *testing.T) {
 		t.Errorf("Content-Type = %q, want 'application/yaml; charset=utf-8'", ct)
 	}
 
+	// Bundle inlines a private key — every cache between server and operator
+	// must drop the response. Mirrors the Web-UI sibling's headers.
+	for header, want := range map[string]string{
+		"Cache-Control":         "no-store",
+		"Pragma":                "no-cache",
+		"Expires":               "0",
+		"X-Content-Type-Options": "nosniff",
+	} {
+		if got := w.Header().Get(header); got != want {
+			t.Errorf("%s = %q, want %q", header, got, want)
+		}
+	}
+
 	// Verify body is valid YAML with expected keys
 	var yamlData map[string]interface{}
 	if err := yaml.Unmarshal(w.Body.Bytes(), &yamlData); err != nil {
```

## Which versions are affected by GHSA-6vgg-xhvh-38ff?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/juev/nebula-mesh` | Go | All versions | 0.3.2 |
| `github.com/juev/nebula-mesh` | Go | All versions | 0.3.2 |
| `github.com/juev/nebula-mesh` | Go | All versions | 0.3.2 |

## How do I fix GHSA-6vgg-xhvh-38ff?

Upgrade github.com/juev/nebula-mesh to 0.3.2 or later.

## Is GHSA-6vgg-xhvh-38ff being exploited?

There is no known exploitation of GHSA-6vgg-xhvh-38ff in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-6vgg-xhvh-38ff and fix it if it is affected.

What it is: GHSA-6vgg-xhvh-38ff is a vulnerability in github.com/juev/nebula-mesh, published on 12 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-6vgg-xhvh-38ff in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/juev/nebula-mesh (Go): affected all versions; fixed in 0.3.2
- github.com/juev/nebula-mesh (Go): affected all versions; fixed in 0.3.2
- github.com/juev/nebula-mesh (Go): affected all versions; fixed in 0.3.2

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/GHSA-6vgg-xhvh-38ff/ (Markdown: https://insights.sbomify.com/GHSA-6vgg-xhvh-38ff/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-6vgg-xhvh-38ff

---
From sbomify Insights: https://insights.sbomify.com/GHSA-6vgg-xhvh-38ff/
Summaries are generated and may contain mistakes; the official description above is the record.