CVE-2026-104851

Name of the Vulnerable Software and Affected Versions fsspec versions 0.9.0 through 2026.6.0

Description The fsspec.implementations.reference.ReferenceFileSystem evaluates fields from Kerchunk reference JSON documents using unrestricted jinja2.Template(...).render(...) calls within the process references1. render jinja, process templates, and process gen functions in fsspec/implementations/reference.py. An attacker can provide a malicious document inline or via a controlled URL containing template expressions that execute arbitrary Python code when the reference filesystem is opened, which can occur through consumers such as xarray before data is read. The process gen path is triggered when a document includes a gen array, while other paths depend on specific template-related options and values.

Recommendations Update fsspec to version 2026.6.0.