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Path TraversalWeakness · CWE-22

CVE-2026-57079

MEDIUM · 5.3 CVSS v3.1 Published 2026-06-30
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click 7 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Net::BitTorrent versions before 2.1.0 suffer from a path traversal vulnerability in the peer/magnet metadata handling path (BEP09 ut_metadata extension). When receiving metadata from peers, file paths from _on_metadata_received are passed directly to Storage::add_file and Storage::_parse_file_tree without validation. Path::Tiny's child() does not sanitize '..' sequences, allowing attackers to write files outside the designated download directory. Since attackers control the piece hashes, content verification passes normally.

MitigationUpgrade to Net::BitTorrent 2.1.0 or later which adds proper path validation for peer-supplied metadata. Until then, avoid using Net::BitTorrent with untrusted peers or implement network-level restrictions on BitTorrent connections.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Find installed Net::BitTorrent version
    Run 'perl -MNet::BitTorrent -e "print $Net::BitTorrent::VERSION"' or check your Perl library installation (e.g., cpan -D Net::BitTorrent, or your system's package manager)
    Affected if version is 2.0.1 or lower (the vulnerability affects all versions through 2.0.1)
  2. Verify ut_metadata extension is in use
    Inspect your Net::BitTorrent configuration or code that initializes the client - look for enable_protocol('ut_metadata') or similar BEP09 metadata extension settings
    Affected if the ut_metadata/ut_metadata extension is enabled, as this is the attack vector that allows malicious peers to supply crafted metadata filenames
  3. Check Storage module configuration
    Examine how Storage is configured in your Net::BitTorrent setup - look for Storage::add_file or Storage::_parse_file_tree usage in logs or configuration to confirm peer-supplied file paths are processed
    Affected if peer metadata can trigger file storage operations, which is the default behavior when ut_metadata is enabled

You are affected if Net::BitTorrent version 2.0.1 or lower is installed AND the ut_metadata (BEP09) extension is enabled, allowing peers to supply metadata that can trigger path traversal in the file storage functions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Net::BitTorrent 2.1.0 or later which adds proper path validation for peer-supplied metadata. Until then, avoid using Net::BitTorrent with untrusted peers or implement network-level restrictions on BitTorrent connections.

Recommended fix High confidence

2.1.0

  1. Check current Net::BitTorrent version by running 'perl -MNet::BitTorrent -e 'print $Net::BitTorrent::VERSION'
  2. Update Net::BitTorrent to version 2.1.0 using cpanm: 'cpanm Net::[email protected]' or 'cpan Net::BitTorrent'
  3. Alternatively, if using a system package manager, update to the package containing version 2.1.0
  4. Verify the new version is installed: 'perl -MNet::BitTorrent -e 'print $Net::BitTorrent::VERSION''
  5. Consult the Net::BitTorrent 2.1.0 release notes for any migration considerations
Caveat Review Net::BitTorrent 2.1.0 release notes for any API or behavior changes that may affect existing code

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,380
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-57079 in production — separate from our analysis above.

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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