CVE-2026-34783: Ferret has a Path Traversal in IO::FS::WRITE allows arbitrary file write when scraping malicious websites

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-06 · updated 2026-10-23
Weakness: CWE-22

Description

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.

Affected products

MontFerret ferret: before 2.0.0; 2.0.0-alpha1, 2.0.0-alpha2, 2.0.0-alpha3 — fixed in 2.0.0

How to fix

Upgrade to a fixed version: MontFerret ferret 2.0.0. Check the vendor advisory for mitigations.

References

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