{"id":"CVE-2026-104851","state":"PUBLISHED","title":"fsspec: Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution","description":"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.","publishedAt":"2026-10-02T16:36:48.513Z","updatedAt":"2026-10-05T20:03:36.502Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["fsspec filesystem_spec"],"affected":[{"vendor":"fsspec","product":"filesystem_spec","versions":[{"version":">= 0.9.0, < 2026.6.0","status":"affected"}]}],"references":["https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc","https://github.com/fsspec/filesystem_spec/pull/2029","https://github.com/fsspec/filesystem_spec/pull/2039","https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611c","https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8","https://github.com/fsspec/filesystem_spec/releases/tag/2026.6.0"],"weaknesses":["CWE-94","CWE-1336"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/104xxx/CVE-2026-104851.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-104851","state":"PUBLISHED","datePublished":"2026-10-02T16:36:48.513Z","dateUpdated":"2026-10-05T20:03:36.502Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-10-02T14:38:43.244Z"},"containers":{"cna":{"title":"fsspec: Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"fsspec","product":"filesystem_spec","versions":[{"version":">= 0.9.0, < 2026.6.0","status":"affected"}]}],"references":[{"url":"https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc","name":"https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/fsspec/filesystem_spec/pull/2029","name":"https://github.com/fsspec/filesystem_spec/pull/2029","tags":["x_refsource_MISC"]},{"url":"https://github.com/fsspec/filesystem_spec/pull/2039","name":"https://github.com/fsspec/filesystem_spec/pull/2039","tags":["x_refsource_MISC"]},{"url":"https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611c","name":"https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611c","tags":["x_refsource_MISC"]},{"url":"https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8","name":"https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8","tags":["x_refsource_MISC"]},{"url":"https://github.com/fsspec/filesystem_spec/releases/tag/2026.6.0","name":"https://github.com/fsspec/filesystem_spec/releases/tag/2026.6.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":8.8,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-94","lang":"en","description":"CWE-94: Improper Control of Generation of Code ('Code Injection')","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1336","lang":"en","description":"CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-10-02T16:36:48.513Z"},"source":{"advisory":"GHSA-27vj-qcqg-25rc","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-05T20:03:10.746838Z","id":"CVE-2026-104851","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-05T20:03:36.502Z"}}]}}}