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

Vulnerability summary

CVE-2026-34783 is a high (CVSS 8.1) vulnerability in montferret ferret. EPSS estimates a 0.52% chance of exploitation in the next 30 days, higher than 44.4% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 06-04-2026
   PublishedVulnerability first disclosed.
2. 07-04-2026
   Last modifiedVulnerability information updated.

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.

• CWE-22Improper Limitation of a Pathname to a Restricted DirectoryThe product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
• CWE-73External Control of File Name or PathThe product allows user input to control or influence paths or file names that are used in filesystem operations.