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Critical, CVSS 9.1amended

Basic FTP has Path Traversal Vulnerability in its downloadToDir() method

CVE-2026-27699GHSA-5rq4-664w-9x2c

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (basic-ftp 5.2.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
9.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
EPSS
  • CVE-2026-27699: 0.94% estimated exploitation activity in the next 30 days; percentile 60.97 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

The basic-ftp library contains a path traversal vulnerability in the downloadToDir() method. A malicious FTP server can send directory listings with filenames containing path traversal sequences (../) that cause files to be written outside the intended download directory. Source-to-Sink Flow Vulnerable Code File: src/Client.ts:707 Root Cause: - Parser validation (parseListUnix.ts:101) only filters exact . or .. entries - No sanitization of ../ sequences in filenames - path.join() doesn't prevent traversal, fs.open() resolves paths Impact A malicious FTP server can: - Write files to arbitrary locations on the client filesystem - Overwrite critical system files (if user has write access) - Potentially achieve remote code execution Affected Versions - Tested: v5.1.0 - Likely: All versions (code pattern exists since initial implementation) Mitigation Workaround: Do not use downloadToDir() with untrusted FTP servers. Fix: Sanitize filenames before use:

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-5rq4-664w-9x2c

  2. Revision 2 · amended ·

    Amended from osv record GHSA-5rq4-664w-9x2c

  3. Revision 1 · created ·

    Published from ghsa record GHSA-5rq4-664w-9x2c

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-27699

Advisory: Basic FTP has Path Traversal Vulnerability in its downloadToDir() method
IDs: CVE-2026-27699, GHSA-5rq4-664w-9x2c
Record: https://patchnext.com/advisories/cve-2026-27699 (revision 3, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: basic-ftp 5.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm basic-ftp: affected < 5.2.0; fixed in 5.2.0

## Suggested inspection (read-only)
- `npm ls basic-ftp --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on basic-ftp.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5rq4-664w-9x2c (GitHub-reviewed advisory GHSA-5rq4-664w-9x2c lists affected ranges: npm basic-ftp >=0 <5.2.0)
- Verified: https://osv.dev/vulnerability/GHSA-5rq4-664w-9x2c (OSV record GHSA-5rq4-664w-9x2c lists affected ranges: npm basic-ftp >=0 <5.2.0 (fixed))

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