High 8.8Published Oct 2, 2026

CVE-2026-104851fsspec: Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution

Updated under an hour ago (Oct 28, 2026, 6:23 PM ET)

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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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Every CVE for fsspec filesystem_spec

Exploited in the last 30 days

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

Affected products

fsspec filesystem_spec fsspec:filesystem_spec (from the name)	from 0.9.0, < 2026.6.0	CNA record

References

References

https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc	x-refsource-confirm
https://github.com/fsspec/filesystem_spec/pull/2029	x-refsource-misc
https://github.com/fsspec/filesystem_spec/pull/2039	x-refsource-misc
https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611c	x-refsource-misc
https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8	x-refsource-misc
https://github.com/fsspec/filesystem_spec/releases/tag/2026.6.0	x-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.