GHSA-27vj-qcqg-25rc: fsspec (CVE-2026-104851)

Package	Ecosystem	Affected	Fixed in
fsspec	PyPI	>=0.9.0, <2026.6.0	2026.6.0

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

GHSA-27vj-qcqg-25rc affects the PyPI package fsspec, versions 0.9.0 up to but not including 2026.6.0. A ReferenceFileSystem reference JSON document, supplied inline or from a URL, is rendered through unsandboxed Jinja2 templates, so an attacker who controls that document can run arbitrary Python code on the victim's machine when it is opened. Upgrade to fsspec 2026.6.0 or later.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
8.8	High	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0047, the 41st percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:08 UTC First seen by agentprime
31 Oct 2026, 14:08 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.