CVE-2026-104851

HIGHPre-NVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (22nd percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 8.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
8.8
EG Score
8.8HIGHmedium confidence
EG Risk
44
EG Risk 44/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity88% × 45%
Exploitation0% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
22nd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

October 2, 2026

Last Modified

October 2, 2026

Advisory Details (5)

Auto-updated Oct 2, 2026
🔬 Proof of concept available. Patch available. Sources: github_pr, github_commit, github.
github_commit

commit a1c16ab3f07f (fsspec/filesystem_spec)

Fix landed in fsspec/filesystem_spec commit a1c16ab3f07f — awaiting tagged release

https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8
github_commit

commit 86438783f93b (fsspec/filesystem_spec)

Fix landed in fsspec/filesystem_spec commit 86438783f93b — awaiting tagged release

https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611c
github_pr

Small safety improvements

Fix merged in fsspec/filesystem_spec PR #2039 on 2026-05-15 — awaiting tagged release

https://github.com/fsspec/filesystem_spec/pull/2039
github_pr

Honour simple_templates everywhere in referenceFS

Fix merged in fsspec/filesystem_spec PR #2029 on 2026-05-15 — awaiting tagged release

https://github.com/fsspec/filesystem_spec/pull/2029
github Patch Available🟡 PoC Available

Server-Side Template Injection in ReferenceFileSystem leads to Remote Code Execution · Advisory · fsspec/filesystem_spec · GitHub

https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 5× in last 7d / 5× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-03 19:08 UTCEG score recompute
  2. 2026-10-03 14:25 UTCEPSS rescore
  3. 2026-10-02 17:29 UTCEG score recompute
  4. 2026-10-02 16:45 UTCEG score recompute
  5. 2026-10-02 16:45 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-104851?
CVE-2026-104851 is a high vulnerability published on October 2, 2026. 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…
When was CVE-2026-104851 disclosed?
CVE-2026-104851 was first published on October 2, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-104851 actively exploited?
CVE-2026-104851 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (22nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-104851?
CVE-2026-104851 has a CVSS base score of 8.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-104851?
A fix for CVE-2026-104851 is available: update to the fixed version the vendor names in its advisory.

Dependency Blast Radius

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