Description
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.
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Remediation
No vendor fix or workaround currently provided.
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References
History
Fri, 02 Oct 2026 16:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | fsspec: Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution | |
| Weaknesses | CWE-1336 CWE-94 |
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cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-10-02T16:36:48.513Z
Reserved: 2026-10-02T14:38:43.244Z
Link: CVE-2026-104851
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