Detect CVE-2026-53633: Vitest Browser Mode API RCE via CDP Proxy and Config Overwrite in Elastic Security
CVE-2026-53633 is a critical (CVSS 9.8) remote code execution vulnerability in @vitest/browser and vite-plus packages. The browser mode API is exposed without adequate authorization controls (CWE-749, CWE-862), allowing unauthenticated attackers to proxy Chrome DevTools Protocol (CDP) commands and overwrite configuration files. This can lead to arbitrary code execution on the host running Vitest in browser mode. Affected versions include @vitest/browser >= 3.0.0 <= 3.2.4, >= 4.0.0 <= 4.1.7, >= 5.0.0-beta.0 <= 5.0.0-beta.3, and vite-plus <= 0.1.23. A public PoC exists.
MITRE ATT&CK
Elastic Detection Query
sequence by source.ip with maxspan=5m
[network where destination.port in (51204, 51205, 5173, 5174, 4173)
and url.path like~ "*__vitest*" or url.path like~ "*/cdp*" or url.path like~ "*/json"]
[network where destination.port in (51204, 51205, 5173, 5174, 4173)
and (url.query like~ "*Runtime.evaluate*"
or url.query like~ "*Page.navigate*"
or url.query like~ "*Target.attachToTarget*"
or url.path like~ "*.config*"
or url.path like~ "*.env*")]EQL sequence detection identifying initial Vitest browser mode API discovery followed by CDP command injection or config file access, characteristic of CVE-2026-53633 multi-step exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Automated test frameworks making sequential API calls to Vitest during legitimate test runs
- Browser developer tools connecting to Vitest WebSocket endpoints during debugging
- Integration test suites that enumerate Vitest API capabilities before test execution
Other platforms for CVE-2026-53633
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Vitest Browser Mode CDP Discovery via /json Endpoint
Expected signal: HTTP GET requests to /json and /__vitest_api__/ on ports 51204 or 5173 from an external source IP visible in web server or proxy logs
- Test 2CDP Runtime.evaluate Arbitrary JavaScript Execution via Vitest Browser API
Expected signal: WebSocket upgrade request to /devtools/page/<id> followed by CDP Runtime.evaluate method in request payload visible in network capture
- Test 3Vitest Config File Overwrite via Exposed API
Expected signal: HTTP POST to /__vitest_api__ with writeFile method in request body; filesystem audit log showing vitest.config.ts modification timestamp updated outside normal developer hours
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