---
id: CVE-2026-57079
title: >-
  Net::BitTorrent versions before 2.1.0 for Perl write files outside the
  download directory via path traversal in peer-supplied metadata.


  Net::BitTorrent validates file path components only on the .torrent-file
  ingest path
summary: >-
  Net::BitTorrent versions before 2.1.0 for Perl write files outside the
  download directory via path traversal in peer-supplied metadata.


  Net::BitTorrent validates file path components only on the .torrent-file
  ingest path. The peer and m…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-22
published: '2026-06-30'
updated: '2026-07-20'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-57079'
references:
  - url: >-
      https://github.com/sanko/Net-BitTorrent.pm/security/advisories/GHSA-5wc6-r65f-62rr
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: 'https://metacpan.org/release/SANKO/Net-BitTorrent-v2.1.0/changes'
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
tags:
  - nvd
epss: 0.00403
epssPercentile: 0.34369
ingestedAt: '2026-07-20T07:36:55.561Z'
---

## Overview

Net::BitTorrent versions before 2.1.0 for Perl write files outside the download directory via path traversal in peer-supplied metadata.

Net::BitTorrent validates file path components only on the .torrent-file ingest path. The peer and magnet metadata path (_on_metadata_received, reached from the BEP09 ut_metadata extension) passes attacker-supplied file names straight to Storage::add_file and Storage::_parse_file_tree, where Path::Tiny's child() does not collapse "..". A v2 file tree key, a v1 files[].path element, or a single-file name containing ".." segments therefore resolves outside the download directory.

Because the peer also controls the piece hashes and the served bytes, content verification passes, so a malicious magnet or peer writes attacker-chosen content to an attacker-chosen path on the downloading host.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.