Disclosure summary
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.
Source-reported weakness categories
CWE-94, CWE-1336
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
GitHub Reviewed Security Advisories · GHSA-27vj-qcqg-25rc
Open original source · Updated Oct 05, 2026
fsspec: Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution
Source severity: HIGH / 0
| Ecosystem | Package | Affected range | First patched |
|---|---|---|---|
| pip | fsspec | >= 0.9.0, < 2026.6.0 | 2026.6.0 |
NIST National Vulnerability Database · NVD-CVE-2026-104851
Open original source · Updated Oct 05, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
Original records & references
- NIST NVD record
- CVE Program record
- github.com
- github.com
- github.com
- github.com
- github.com
- github.com
- github.com
PUBLISHED 2026-10-02T13:17:03-04:00
MODIFIED 2026-10-05T16:17:09-04:00
INGESTED 2026-10-06T11:45:30-04:00