{"id":"UBUNTU-CVE-2026-104851","details":"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.","modified":"2026-10-05T13:04:12.072338268Z","published":"2026-10-05T00:00:00Z","upstream":["CVE-2026-104851"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-104851"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-104851"},{"type":"REPORT","url":"https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc"},{"type":"REPORT","url":"https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611c"},{"type":"REPORT","url":"https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8"},{"type":"REPORT","url":"https://github.com/fsspec/filesystem_spec/pull/2029"},{"type":"REPORT","url":"https://github.com/fsspec/filesystem_spec/pull/2039"},{"type":"REPORT","url":"https://github.com/fsspec/filesystem_spec/releases/tag/2026.6.0"}],"affected":[{"package":{"name":"fsspec","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/fsspec?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.1-0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-fsspec","binary_version":"0.6.1-0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-104851.json"}},{"package":{"name":"fsspec","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/fsspec?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.4-1","2022.01.0-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-fsspec","binary_version":"2022.01.0-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-104851.json"}},{"package":{"name":"fsspec","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/fsspec?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2023.6.0-1","2023.9.2-1","2023.10.0-1","2024.2.0-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-fsspec","binary_version":"2024.2.0-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-104851.json"}},{"package":{"name":"fsspec","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/fsspec?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2025.3.2-1ubuntu1","2025.12.0-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-fsspec","binary_version":"2025.12.0-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-104851.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}