# CVE-2026-57079: Path traversal in Net::BitTorrent

> A malicious peer can write arbitrary files outside the download directory via path traversal in metadata, potentially leading to code execution.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Jun 2026
- **Updated:** 20 Jul 2026
- **Also known as:** GHSA-5gfq-2rx4-6vwv, GHSA-5wc6-r65f-62rr

## What is CVE-2026-57079?

CVE-2026-57079 is a medium-severity path traversal vulnerability in SANKO Net::BitTorrent, published on 30 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-57079?


## How do I fix CVE-2026-57079?

No fix has been published for CVE-2026-57079 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-57079 being exploited?

There is no known exploitation of CVE-2026-57079 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57079 and fix it if it is affected.

What it is: CVE-2026-57079 is a medium-severity path traversal vulnerability in SANKO Net::BitTorrent, published on 30 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-57079 in the wild and no public exploit code.

Affected product: SANKO Net::BitTorrent. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-57079/ (Markdown: https://insights.sbomify.com/CVE-2026-57079/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57079
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57079
- OSV: https://osv.dev/vulnerability/CVE-2026-57079

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-57079/
Summaries are generated and may contain mistakes; the official description above is the record.