CVE-2026-73653 is a critical-severity (CVSS 9.4) Path Traversal vulnerability in @vitest/browser. O3 Security confirms whether CVE-2026-73653 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
@vitest/browser: Browser Mode provider commands bypass the file-access permission gate
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-73653.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@vitest/browsernpmDescription
Summary
Browser Mode exposes a set of built-in "commands" that run on the Node.js side of the test runner and can touch the local filesystem (taking screenshots, managing Playwright traces, uploading files for <input type="file">, comparing screenshots).
Several of these commands accept a file path from the browser and act on it without checking the allowWrite permission gate and without confining the path to the project directory. A client that can reach the Browser Mode API can therefore read, create, overwrite, or delete files anywhere the Vitest process can access, even when allowWrite is false.
This matters most when the Browser Mode API is exposed to the network (for example test.api.host is set, or the dev server is reachable from another machine or origin). In that configuration allowWrite defaults to false precisely to block file access, and these commands bypass that protection. On a default localhost-only setup with trusted test code, there is no untrusted party in a position to exploit it. The gap still matters wherever you rely on allowWrite: false to contain untrusted test code, because these commands ignore that flag.
Affected commands and impact
| Command | Operation | Impact |
|---|---|---|
upload (Playwright + WebdriverIO) | Read | Arbitrary local file read; contents are loaded into the page and readable by test code. Highest-impact case. |
takeScreenshot (Playwright + WebdriverIO) | Write | Writes a PNG to an arbitrary path (absolute path used verbatim), creating parent directories. |
screenshotMatcher | Write | Writes reference/diff PNGs; directory derived from client path allows partial traversal. |
stopChunkTrace | Write | Writes a Playwright trace .zip to a path escapable via ../ in the trace name. |
deleteTracing | Delete | Deletes arbitrary files by path. |
annotateTraces | Read (disclosure) | Records a client-controlled attachment path that the reporter copies into the attachments directory, disclosing file contents. |
The writes do not let an attacker choose the file contents (they produce PNG images or trace archives), so the integrity impact is creating, overwriting, or deleting a file at an arbitrary path rather than writing a chosen payload. The reads (upload, annotateTraces) are more serious because they expose the full contents of an arbitrary file.
The fix adds, to every file-touching provider command, an allowWrite check for write/delete operations and path confinement to the project root (matching the existing fs command pattern), so client-supplied absolute paths and ../ traversal are rejected.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @vitest/browser | ≥ 4.0.0&&< 4.1.10 | 4.1.10 |
| 📦npm | @vitest/browser | all versions | 3.2.7 |
| 📦npm | @vitest/browser | ≥ 5.0.0-beta.1&&< 5.0.0-beta.6 | 5.0.0-beta.6 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @vitest/browser. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @vitest/browser to 4.1.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-73653 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-73653 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-73653. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-73653 in your dependencies?
O3 detects CVE-2026-73653 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.