CVE-2026-112948

Vitest is a testing framework powered by Vite. From 5.0.0-beta.6 until 5.0.5, Vitest dev servers can misapply server.fs.deny because project servers replace Vite's defaults and the root server adds .vitest-secret-token after Vite compiles its matcher. An attacker who can reach an affected UI, Browser Mode, or API server can read denied project files or the fallback API token at node_modules/.vitest/.vitest-secret-token, and Browser Mode with test.projects can expose JavaScript-compatible .env values through a malicious website. This issue is fixed in version 5.0.5.

Vitest is a testing framework powered by Vite. From 5.0.0-beta.6 until 5.0.5, Vitest dev servers can misapply server.fs.deny because project servers replace Vite's defaults and the root server adds .vitest-secret-token after Vite compiles its matcher. An attacker who can reach an affected UI, Browser Mode, or API server can read denied project files or the fallback API token at node_modules/.vitest/.vitest-secret-token, and Browser Mode with test.projects can expose JavaScript-compatible .env values through a malicious website. This issue is fixed in version 5.0.5.

Summary

In Vitest 5, Vite's server.fs.deny is not applied as intended on Vitest's dev servers. Depending on the server, files that Vite refuses to serve by default (such as .env, private keys and certificates, .npmrc, and .git) or Vitest's own API token file (.vitest-secret-token) can be read over plain HTTP by a client that can reach the server. In Browser Mode with test.projects, a malicious website can also read .env values through the developer's browser.

This only applies when Vitest runs an HTTP server, which happens with the UI (--ui), Browser Mode, or api enabled. Plain vitest and vitest run don't listen on any port and are not affected. The fix ships in vitest, and @vitest/ui and @vitest/browser are listed because they are what enables the affected setups. Both pin vitest to the same version as a peer dependency, so upgrading either one also requires the patched vitest. Users who enable api without @vitest/ui or @vitest/browser are also affected and should upgrade vitest.

Details

Vitest 5 adds its API token file to server.fs.deny, but neither server ended up with the intended list. That's because of two Vite behaviors. Vite applies its default deny list only when server.fs.deny is unset, and it compiles the list into a matcher during config resolution, so later changes to the array have no effect.

| setup | listening server | Vite's default deny list | .vitest-secret-token | | ---------------------------------- | ------------------------------- | ------------------------ | ----------------------------------- | | plain vitest / vitest run | none | not reachable | not reachable | | --ui or api | root | denied | served (fallback location only) | | Browser Mode, single project | root (also the browser server) | denied | served (fallback location only) | | Browser Mode with test.projects | each browser project's server | served | denied |

• Project servers set deny: ['.vitest-secret-token'] from a config() hook, which replaces Vite's defaults. A project server listens on a port in Browser Mode with test.projects, so in that setup a request like GET /.env?raw returns the file. A plain GET /.env is also served as text/javascript, so a malicious page can include it with <script src="http://localhost:<port>/.env">. A classic script include needs no CORS, and each dotenv line whose value is valid JavaScript (a quoted string, number, or boolean) runs as a global assignment the page can read. A syntax error anywhere in the file, such as a # comment, keeps the whole script from running. The same missing defaults also loosen Browser Mode's file-access checks for server.readFile/writeFile/removeFile, screenshots, and traces.
• The root server adds the token entry after Vite has compiled the matcher, so the entry is never applied. The token file normally lives in the per-user data directory, which is outside server.fs.allow. When that directory can't be written, for example in a container whose user has no writable HOME, Vitest falls back to <workspaceRoot>/node_modules/.vitest/.vitest-secret-token, which the root server then serves. The token authenticates the UI, /__vitest_attachment__, and the API WebSocket, whose RPC can write and rerun test files when api.allowWrite/api.allowExec are enabled.

Impact

Information disclosure from the Vitest dev server, and with the token, privileged API access.

• From a malicious website, in Browser Mode with test.projects: while the browser server runs, any page the developer visits can read .env values that are valid JavaScript, through a classic <script> include. This works when the file consists of…

Vitest is a testing framework powered by Vite. From 5.0.0-beta.6 until 5.0.5, Vitest dev servers can misapply server.fs.deny because project servers replace Vite's defaults and the root server adds .vitest-secret-token after Vite compiles its matcher. An attacker who can reach an affected UI, Browser Mode, or API server can read denied project files or the fallback API token at node_modules/.vitest/.vitest-secret-token, and Browser Mode with test.projects can expose JavaScript-compatible .env values through a malicious website. This issue is fixed in version 5.0.5.

Vitest is a testing framework powered by Vite. From 5.0.0-beta.6 until 5.0.5, Vitest dev servers can misapply server.fs.deny because project servers replace Vite's defaults and the root server adds .vitest-secret-token after Vite compiles its matcher. An attacker who can reach an affected UI, Browser Mode, or API server can read denied project files or the fallback API token at node_modules/.vitest/.vitest-secret-token, and Browser Mode with test.projects can expose JavaScript-compatible .env values through a malicious website. This issue is fixed in version 5.0.5.

Summary

In Vitest 5, Vite's server.fs.deny is not applied as intended on Vitest's dev servers. Depending on the server, files that Vite refuses to serve by default (such as .env, private keys and certificates, .npmrc, and .git) or Vitest's own API token file (.vitest-secret-token) can be read over plain HTTP by a client that can reach the server. In Browser Mode with test.projects, a malicious website can also read .env values through the developer's browser.

This only applies when Vitest runs an HTTP server, which happens with the UI (--ui), Browser Mode, or api enabled. Plain vitest and vitest run don't listen on any port and are not affected. The fix ships in vitest, and @vitest/ui and @vitest/browser are listed because they are what enables the affected setups. Both pin vitest to the same version as a peer dependency, so upgrading either one also requires the patched vitest. Users who enable api without @vitest/ui or @vitest/browser are also affected and should upgrade vitest.

Details

Vitest 5 adds its API token file to server.fs.deny, but neither server ended up with the intended list. That's because of two Vite behaviors. Vite applies its default deny list only when server.fs.deny is unset, and it compiles the list into a matcher during config resolution, so later changes to the array have no effect.

| setup | listening server | Vite's default deny list | .vitest-secret-token | | ---------------------------------- | ------------------------------- | ------------------------ | ----------------------------------- | | plain vitest / vitest run | none | not reachable | not reachable | | --ui or api | root | denied | served (fallback location only) | | Browser Mode, single project | root (also the browser server) | denied | served (fallback location only) | | Browser Mode with test.projects | each browser project's server | served | denied |

• Project servers set deny: ['.vitest-secret-token'] from a config() hook, which replaces Vite's defaults. A project server listens on a port in Browser Mode with test.projects, so in that setup a request like GET /.env?raw returns the file. A plain GET /.env is also served as text/javascript, so a malicious page can include it with <script src="http://localhost:<port>/.env">. A classic script include needs no CORS, and each dotenv line whose value is valid JavaScript (a quoted string, number, or boolean) runs as a global assignment the page can read. A syntax error anywhere in the file, such as a # comment, keeps the whole script from running. The same missing defaults also loosen Browser Mode's file-access checks for server.readFile/writeFile/removeFile, screenshots, and traces.
• The root server adds the token entry after Vite has compiled the matcher, so the entry is never applied. The token file normally lives in the per-user data directory, which is outside server.fs.allow. When that directory can't be written, for example in a container whose user has no writable HOME, Vitest falls back to <workspaceRoot>/node_modules/.vitest/.vitest-secret-token, which the root server then serves. The token authenticates the UI, /__vitest_attachment__, and the API WebSocket, whose RPC can write and rerun test files when api.allowWrite/api.allowExec are enabled.

Impact

Information disclosure from the Vitest dev server, and with the token, privileged API access.

• From a malicious website, in Browser Mode with test.projects: while the browser server runs, any page the developer visits can read .env values that are valid JavaScript, through a classic <script> include. This works when the file consists of…