Fallow: Jest and Vitest `projects` entries let an analyzed repository make Fallow read files outside the project root

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Fallow is a codebase intelligence tool for TypeScript and JavaScript. From 2.68.0 until 3.34.0, Fallow follows attacker-controlled Jest projects paths outside the project root through absolute paths, parent segments, dot-prefixed wildcard globs, or symlinks. In version 3.33.1, the same behavior also affects Vitest test.projects paths, Vitest inline-project extends paths, and symlinked script --config paths. Fallow parses the outside files as test-runner configuration and uses them to credit dependencies, setup files, and JSX import sources, which can change unused dependency and unused file findings in CI or agent analysis. The outside file contents are not printed or sent over the network. This issue is fixed in version 3.34.0.

Source published

23 Oct 2026 18:09:47 UTC

Source modified

23 Oct 2026 18:09:47 UTC

Observed here

23 Oct 2026 19:48:20 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 3.3 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Fallow is a codebase intelligence tool for TypeScript and JavaScript. From 2.68.0 until 3.34.0, Fallow follows attacker-controlled Jest projects paths outside the project root through absolute paths, parent segments, dot-prefixed wildcard globs, or symlinks. In version 3.33.1, the same behavior also affects Vitest test.projects paths, Vitest inline-project extends paths, and symlinked script --config paths. Fallow parses the outside files as test-runner configuration and uses them to credit dependencies, setup files, and JSX import sources, which can change unused dependency and unused file findings in CI or agent analysis. The outside file contents are not printed or sent over the network. This issue is fixed in version 3.34.0.

Source published

23 Oct 2026 19:17:44 UTC

Source modified

23 Oct 2026 19:57:42 UTC

Observed here

25 Oct 2026 05:17:25 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 3.3 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

### Impact Fallow reads the Jest and Vitest configs of the repository that it analyzes. A Jest `projects` entry or a Vitest `test.projects` entry can name a path. Fallow followed such an entry to a config file and read that file, also when the file was outside the project root. These forms reached outside the root: - an absolute path or glob, for example `/etc/*`; - a path with `..` segments, for example `../*`; - a glob with a `.*` segment, because the `glob` crate also tests `..` against a segment that starts with a literal `.`; - a symlink in the project root to a directory above it; - the `extends` path of a Vitest inline project; - a script `--config` path that is a symlink to a file outside the project root. Fallow parsed each of these files as a test runner config. Fallow used the content only to credit dependencies, setup files and JSX import sources. Thus unused dependency and unused file findings could change. Fallow did not print the content or send it over the network. The Fallow threat model states that analysis reads only inside the project root. A crafted repository could make Fallow read files that the user did not expect. Such a read can happen in CI, or when an agent runs Fallow on a cloned repository. The attacker gets changed findings, not the file content. Versions 2.68.0 to 3.33.1 read outside files through Jest `projects`. Version 3.33.1 also read them through Vitest `test.projects`. ### Patches Fixed in 3.34.0. Fallow now resolves each match with symlinks and `..` segments removed. Fallow reads the match only when it is inside the project root. A glob whose literal base is outside the project root does not run. The boundary is the project root, so an in-root entry such as `<rootDir>/../packages/*` still works, also from the config of a workspace package. Fallow also does not read a script `--config` path that is a symlink to a file outside the project root. ### Workarounds Run Fallow only on repositories that you trust. Before you run Fallow on another repository, check the `projects` entries of its `jest.config.*` and `vitest.config.*` files.

Source published

23 Oct 2026 21:57:37 UTC

Source modified

23 Oct 2026 22:15:04 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Publisher rating · LOW