CVE-2026-104851fsspec: Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution
Updated under an hour ago ()
Does this affect you?
It affects fsspec filesystem_spec. Add what you run to find out whether that includes you.
EPSS puts the chance of exploitation in the next 30 days at 0.32%, higher than 23% of scored CVEs.
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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.
- CVSS
- 8.8 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-94, CWE-1336
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- 0.32% (percentile 23)
- Assigned by
- GitHub_M
- NVD analysis
- Deferred
- Record last updated
- Oct 5, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
fsspec filesystem_spec fsspec:filesystem_spec (from the name) | from 0.9.0, < 2026.6.0 | CNA record |
References
- https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rcx-refsource-confirm
- https://github.com/fsspec/filesystem_spec/pull/2029x-refsource-misc
- https://github.com/fsspec/filesystem_spec/pull/2039x-refsource-misc
- https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611cx-refsource-misc
- https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8x-refsource-misc
- https://github.com/fsspec/filesystem_spec/releases/tag/2026.6.0x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.