{"id":"CVE-2026-104851","summary":"fsspec: Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution","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.","aliases":["GHSA-27vj-qcqg-25rc"],"modified":"2026-10-04T02:46:03.482499552Z","published":"2026-10-02T16:36:48.513Z","database_specific":{"cwe_ids":["CWE-1336","CWE-94"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/104xxx/CVE-2026-104851.json","cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://github.com/fsspec/filesystem_spec/releases/tag/2026.6.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/104xxx/CVE-2026-104851.json"},{"type":"ADVISORY","url":"https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-104851"},{"type":"FIX","url":"https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611c"},{"type":"FIX","url":"https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8"},{"type":"FIX","url":"https://github.com/fsspec/filesystem_spec/pull/2029"},{"type":"FIX","url":"https://github.com/fsspec/filesystem_spec/pull/2039"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/fsspec/filesystem_spec","events":[{"introduced":"c7d996685de74d2e3dc7f68b3c4722842a6914bc"},{"fixed":"86438783f93b1398ef245b92f0e6063b445b611c"},{"fixed":"a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8"},{"fixed":"a2457004d03e0312f715f90f58873de5ab195a37"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0.9.0"},{"fixed":"2026.6.0"}]}}],"versions":["2026.4.0","2026.3.0","2026.2.0","2026.1.0","2025.12.0","2025.10.0","2025.9.0","2025.7.0","2025.5.1","2025.5.0","2025.3.2","2025.3.1","2025.3.0","2025.2.0","2024.12.0","2024.10.0","2024.9.0","2024.6.1","2024.6.0","2024.5.0","2024.3.1","2024.3.0","2024.2.0","2023.12.2","2023.12.1","2023.12.0","2023.10.0","2023.9.2","2023.9.1","2023.9.0","2023.6.0","2023.5.0","2023.4.0","2023.3.0","2023.1.0","2022.11.0","2022.10.0","2022.8.2","2022.8.1","2022.8.0","2022.7.1","2022.7.0","2022.5.0","2022.3.0","2022.02.0","2022.01.0","2021.11.1","2021.11.0","2021.10.1","2021.10.0","2021.09.0","2021.08.1","2021.07.0","2021.06.1","2021.06.0","2021.05.0","2021.04.0","0.9.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/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"}]}