adm-zip is a JavaScript library for creating and extracting ZIP archives in Node.js. Prior to 0.6.1, adm-zip applies the Unix permission bits stored in a zip entry directly to the extracted file via `fs.chmodSync()` when `keepOriginalPermission=true` is passed to `extractAllTo()`/`extractEntryTo()` — and it never filters the setuid/setgid/sticky bits out of those bits. A zip crafted by an attacker can therefore produce an extracted binary with mode `04755`. When extraction runs as root (the default posture in Docker builds, CI runners, and privileged install steps — the exact environments where this flag is used), the resulting root-owned setuid file is executed later by a lesser-privileged user, turning the attacker's code into a root execution. Version 0.6.1 fixes the issue.

Affected: npm: adm-zip

## Summary

adm-zip applies the Unix permission bits stored in a zip entry directly to the extracted file via `fs.chmodSync()` when `keepOriginalPermission=true` is passed to `extractAllTo()`/`extractEntryTo()` — and it never filters the setuid/setgid/sticky bits out of those bits. A zip crafted by an attacker can therefore produce an extracted binary with mode `04755`. When extraction runs as root (the default posture in Docker builds, CI runners, and privileged install steps — the exact environments where this flag is used), the resulting root-owned setuid file is executed later by a lesser-privileged user, turning the attacker's code into a root execution.

## Details

The mode a zip entry wants is read back from the external file attributes in the header, and the mask used keeps every special bit:

```js // headers/entryHeader.js:187 get fileAttr() { return (_attr || 0) >> 16 & 0xfff; } ```

`0xfff` is `0o7777` — it preserves setuid (`0o4000`), setgid (`0o2000`) and the sticky bit (`0o1000`) along with the rwx bits. Shifting by 16 is the standard Unix convention for where zip stores the mode; the mask is the problem.

When the flag is on, that value goes straight to the write:

```js // adm-zip.js:726-727 (extractEntryTo, and identically in extractAllTo) const fileAttr = keepOriginalPermission ? entry.header.fileAttr : undefined; filetools.writeFileTo(target, content, overwrite, fileAttr); ```

```js // util/utils.js:94 self.fs.chmodSync(path, attr || 0o666); ```

No…