Security Digest · Vulnerability record
CVE-2026-53633: Vitest Browser: Exposed Browser Mode API Can Proxy CDP and Overwrite Config Files, Leading to RCE
Vitest is a testing framework powered by Vite.
CVSS 9.8 Critical EPSS 0.9% · p59
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.9%, percentile 59: FIRST’s model estimates a 0.9% chance of exploitation activity in the next 30 days, higher than 59% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
@vitest/browser(npm) >= 5.0.0-beta.0, <= 5.0.0-beta.3, fixed in 5.0.0-beta.4;@vitest/browser(npm) >= 4.0.0, <= 4.1.7, fixed in 4.1.8;@vitest/browser(npm) >= 3.0.0, <= 3.2.4, fixed in 3.2.5;vite-plus(npm) <= 0.1.23, fixed in 0.1.24. Check your lockfile, including transitive dependencies.
What it is
Vitest is a testing framework powered by Vite. From 3.0.0 until 3.2.5, 4.1.8, and 5.0.0-beta.4, Vitest Browser Mode exposed a cdp() API that forwarded raw Chrome DevTools Protocol methods without being gated by allowWrite or allowExec, allowing a remote client with exposed browser API metadata to use CDP Page.setDownloadBehavior and Runtime.evaluate to overwrite vite.config.ts and execute attacker-controlled Node.js code. This issue is fixed in versions 3.2.5, 4.1.8, and 5.0.0-beta.
From the GitHub advisory
Summary
Vitest Browser Mode exposes a cdp() API that forwards raw Chrome DevTools Protocol (CDP) methods over the Vitest browser WebSocket RPC. CDP is not gated by browser.api.allowWrite, browser.api.allowExec, api.allowWrite, or api.allowExec.
As a result, disabling Browser Mode write and exec operations does not prevent a browser API client from using CDP to perform equivalent actions. In a verified reproduction with allowWrite: false and allowExec: false, CDP Page.setDownloadBehavior set the browser download directory to the project root, and CDP Runtime.evaluate downloaded a controlled vite.config.ts. Vitest reloaded the changed config and executed attacker-controlled Node.js code.
When the Browser Mode API is also exposed to the network, this becomes remotely exploitable because the generated browser runner page exposes the API token, active session id, project name, and project root path needed to connect to the browser WebSocket API and select the target download directory.
Impact
Weakness type: CWE-749, CWE-862.
Product: @vitest/browser (npm) · Assigned by: GitHub_M · Published: 2026-07-14
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| npm | @vitest/browser | >= 5.0.0-beta.0, <= 5.0.0-beta.3 | 5.0.0-beta.4 |
| npm | @vitest/browser | >= 4.0.0, <= 4.1.7 | 4.1.8 |
| npm | @vitest/browser | >= 3.0.0, <= 3.2.4 | 3.2.5 |
| npm | vite-plus | <= 0.1.23 | 0.1.24 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| vitest-dev | vitest | >= 3.0.0, < 3.2.5, >= 4.0.0, < 4.1.8, >= 5.0.0-beta.0, < 5.0.0-beta.4 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| GitHub | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.90% probability of exploitation activity in the next 30 days; percentile 59.
Timeline
- — GitHub-reviewed advisory GHSA-g8mr-85jm-7xhm published (critical)
- — CVE record published by GitHub_M
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-g8mr-85jm-7xhm github.com
- CVE.org record CVE-2026-53633 cve.org
- NVD entry CVE-2026-53633 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com