Ferret: Path Traversal in IO::FS::WRITE allows arbitrary file write when scraping malicious websites

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

EPSS

• CVE-2026-34783: 0.52% estimated exploitation activity in the next 30 days; percentile 44.43 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 authorizedkeys, 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: 2. The victim runs a standard scraping script: 3. FQL string concatenation produces:…

Published by the source

1 Apr 2026, 23:37 UTC

Last modified by the source

6 Apr 2026, 23:25 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-j6v5-g24h-vg4j

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# Patch Next advisory brief: CVE-2026-34783

Advisory: Ferret: Path Traversal in IO::FS::WRITE allows arbitrary file write when scraping malicious websites
IDs: CVE-2026-34783, GHSA-j6v5-g24h-vg4j
Record: https://patchnext.com/advisories/cve-2026-34783 (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/MontFerret/ferret/v2 2.0.0-alpha.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/MontFerret/ferret: affected <= 0.18.1
- Go github.com/MontFerret/ferret/v2: affected < 2.0.0-alpha.4; fixed in 2.0.0-alpha.4

## Suggested inspection (read-only)
- Go github.com/MontFerret/ferret: check the installed version with your package manager.
- Go github.com/MontFerret/ferret/v2: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/MontFerret/ferret, github.com/MontFerret/ferret/v2.
- 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-j6v5-g24h-vg4j (GitHub-reviewed advisory GHSA-j6v5-g24h-vg4j lists affected ranges: Go github.com/MontFerret/ferret/v2 >=0 =0 <=0.18.1)

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