A flaw in Node.js Permission Model filesystem enforcement leaves `fs.realpathSync()` without the required read permission checks. This is an incomplete fix of CVE-2026-21715, which only covered `fs.realpathSync.native()`. As a result, code running under `--permission` with restricted `--allow-fs-read` can still use `fs.realpathSync()` to check file existence, resolve symlink targets, and enumerate filesystem paths outside of permitted directories. This vulnerability affects Node.js 26.x, 24.x, and 22.x.

LowVendor CVSS 3.3 / 10 2 CVEs Published Oct 25, 2026 at 1:01 AM UTC

Summary

Mariner

Release Notes

Oct 25, 2026 at 1:01 AM UTC
Published by Microsoft Security Response Center
The publication date reported by the vendor.
Oct 26, 2026 at 2:49 PM UTC
Updated by Microsoft Security Response Center
The vendor changed the advisory after it was first published.
Oct 27, 2026 at 9:20 AM UTC
Added to SecurityAlert
We collected the advisory from the official source.
Oct 27, 2026 at 9:40 PM UTC
Confirmed at the source
Our collector saw this advisory during a later source check.

Details collected from Microsoft Security Response Center.

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