fsspec: Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution
fsspec is a specification and Python implementation framework for filesystem interfaces. From 0.9.0 until 2026.6.0, fsspec.implementations.reference.ReferenceFileSystem evaluates fields from Kerchunk reference JSON documents through unrestricted jinja2.Template(...).render(...) calls in _process_references1._render_jinja, _process_templates, and _process_gen in fsspec/implementations/reference.py. A document supplied inline or fetched from an attacker-controlled URL can provide template expressions that execute Python code when the reference filesystem is opened, including through consumers such as xarray, before referenced data is read. The _process_gen path is reached whenever a document includes a gen array, while the other paths depend on template-related options and values. This issue is fixed in version 2026.6.0.
CVE-2026-104851
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-104851
filesystem_spec
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "fsspec",
"product": "filesystem_spec",
"versions": [
{
"status": "affected",
"version": ">= 0.9.0, < 2026.6.0"
}
]
}
]- Related CVEs
- CVE-2026-104851
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #8920 · Revision 1
- Added to Heist Feed
- Publisher date