launch-editor: `fs.existsSync()` existence check can be bypassed on Windows

### Summary `launch-editor` checked `fs.existsSync(fileName)` before passing a supplied path to an editor command. On Windows, an attacker can bypass this check with a crafted path ending in `\\..:line:column`. This removes the requirement that the attacker be able to place a file with a malicious filename. Combined with the `%` escaping issue described in [GHSA-698v-4r3x-3vcv](https://github.com/vitejs/launch-editor/security/advisories/GHSA-698v-4r3x-3vcv), this bypass can lead to OS command injection when an attacker controls the file argument. ### Impact Only apps that runs on Windows is affected. ### Details The earlier advisory assumed that `fs.existsSync()` required an attacker-controlled filename to exist. This advisory covers a bypass of that requirement. A crafted value ending in `\\..:1:1` is interpreted differently by `launch-editor-middleware`, `launch-editor`, and Windows: 1. `launch-editor-middleware` calls `path.resolve()` while the final path component is `..:1:1`, so it is not treated as a parent-directory component. 2. `launch-editor` treats `:1:1` as a line-and-column suffix and removes it, leaving a path ending in `\\..`. 3. On Windows, `fs.existsSync()` accepts the resulting path as the existing parent directory even though the attacker-controlled preceding component does not exist. 4. Because the existence check passes, the crafted filename reaches the Windows shell command.

Source published

20 Oct 2026 19:48:25 UTC

Source modified

20 Oct 2026 20:00:04 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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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_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Publisher rating · HIGH