Bug 2545294 (CVE-2026-104851)

Summary:	CVE-2026-104851 fsspec: fsspec: arbitrary code execution via unrestricted template rendering in ReferenceFileSystem
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	alinfoot, anpicker, anthomas, bbrownin, dfreiber, drow, dschmidt, dtrifiro, ebourniv, ehelms, ggainey, hasun, ilpinto, jburrell, jdobes, jfula, jholecek, jlanda, jowilson, jpasqual, juwatts, jwong, kshier, ltomasbo, mdellweg, mhulan, nmoumoul, nyancey, omaciel, ometelka, orabin, osousa, pcreech, ptisnovs, rbobbitt, rchan, sbunciak, simaishi, smallamp, stcannon, syedriko, tmalecek, vkumar, weaton, xdharmai, yguenane, ykashtan, zzhou
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in fsspec. This vulnerability can lead to arbitrary code execution due to unrestricted template evaluation in the ReferenceFileSystem component. When processing filesystem reference metadata documents, template expressions are evaluated without security restrictions or sandboxing. A remote attacker can exploit this flaw by enticing a user or automated service to open a maliciously crafted reference file, resulting in arbitrary code execution with the privileges of the running application.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Description OSIDB Bzimport 2026-10-02 16:52:37 UTC

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.