CVE-2026-86258

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreHIGH confidence

Score 5.9 from GitHub Security Advisory (severity: HIGH) published 2026-09-06. the CNA's CVSS baseline 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Trending — 3 sources updated this week
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 5.9Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

nbviewer through 1.0.1 contains a path traversal vulnerability in LocalFileHandler.can_show() that uses string-prefix comparison instead of proper path validation. Attackers can read files from sibling directories outside the configured root by requesting paths that share the root as a textual prefix, disclosing unintended notebooks and credentials.

CVSS v3
5.9
EG Score
5.9(high)
EG Risk
27(Track)
EG Risk 27/100SSVC: Track

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
Severity59% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
42%
KEV
Not listed

Published

September 6, 2026

Last Modified

September 24, 2026

Advisory Details (5)

Auto-updated Sep 6, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
generic

nbviewer through 1.0.1 Path Traversal via LocalFileHandler | Advisories | VulnCheck

https://www.vulncheck.com/advisories/nbviewer-through-1.0.1-path-traversal-via-localfilehandler
generic

GitHub - jupyter/nbviewer: nbconvert as a web service: Render Jupyter Notebooks as static web pages · GitHub

https://github.com/jupyter/nbviewer
github_commit

commit aad36106f72a (jupyter/nbviewer)

Fix landed in jupyter/nbviewer commit aad36106f72a — awaiting tagged release

https://github.com/jupyter/nbviewer/commit/aad36106f72a1ca7721310c6fccc677ce4c744a5
generic

nbviewer/nbviewer/providers/local/handlers.py at 1.0.1 · jupyter/nbviewer · GitHub

https://github.com/jupyter/nbviewer/blob/1.0.1/nbviewer/providers/local/handlers.py#L92-L107
generic

nbviewer LocalFileHandler Prefix-Path Containment Bypass Allows Reading Files from Sibling Directories · Issue #1115 · jupyter/nbviewer · GitHub

https://github.com/jupyter/nbviewer/issues/1115

Vendor Advisories for CVE-2026-86258(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 20× in last 7d / 55× 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. 2026-09-24 14:53 UTCEG score recompute
  2. 2026-09-24 14:53 UTCGHSA enrichment
  3. 2026-09-24 14:04 UTCEPSS rescore
  4. 2026-09-24 03:06 UTCEG score recompute
  5. 2026-09-24 03:06 UTCGHSA enrichment
  6. 2026-09-23 17:54 UTCEPSS rescore
  7. 2026-09-23 02:20 UTCEG score recompute
  8. 2026-09-23 02:20 UTCGHSA enrichment
  9. 2026-09-22 16:01 UTCEPSS rescore
  10. 2026-09-22 01:33 UTCEG score recompute
  11. 2026-09-22 01:33 UTCGHSA enrichment
  12. 2026-09-21 21:09 UTCEPSS rescore
  13. 2026-09-21 00:47 UTCEG score recompute
  14. 2026-09-21 00:47 UTCGHSA enrichment
  15. 2026-09-20 20:16 UTCEPSS rescore
  16. 2026-09-20 00:00 UTCEG score recompute
  17. 2026-09-20 00:00 UTCGHSA enrichment
  18. 2026-09-18 23:13 UTCEG score recompute
  19. 2026-09-18 23:13 UTCGHSA enrichment
  20. 2026-09-18 19:28 UTCEPSS rescore
  21. 2026-09-17 22:27 UTCEG score recompute
  22. 2026-09-17 22:27 UTCGHSA enrichment
  23. 2026-09-17 19:32 UTCEPSS rescore
  24. 2026-09-16 21:41 UTCEG score recompute
  25. 2026-09-16 21:41 UTCGHSA enrichment
Show 30 more
  1. 2026-09-16 14:09 UTCEPSS rescore
  2. 2026-09-16 05:15 UTCEPSS rescore
  3. 2026-09-15 20:52 UTCEG score recompute
  4. 2026-09-15 20:52 UTCGHSA enrichment
  5. 2026-09-15 03:12 UTCEPSS rescore
  6. 2026-09-15 03:12 UTCEPSS rescore
  7. 2026-09-14 19:45 UTCGHSA enrichment
  8. 2026-09-13 18:59 UTCEG score recompute
  9. 2026-09-13 18:59 UTCGHSA enrichment
  10. 2026-09-12 18:12 UTCEG score recompute
  11. 2026-09-12 18:12 UTCGHSA enrichment
  12. 2026-09-11 17:25 UTCEG score recompute
  13. 2026-09-11 17:25 UTCGHSA enrichment
  14. 2026-09-11 14:53 UTCEPSS rescore
  15. 2026-09-11 14:53 UTCEPSS rescore
  16. 2026-09-10 16:25 UTCEG score recompute
  17. 2026-09-10 16:25 UTCGHSA enrichment
  18. 2026-09-10 15:27 UTCEG score recompute
  19. 2026-09-10 15:27 UTCGHSA enrichment
  20. 2026-09-09 23:19 UTCEG score recompute
  21. 2026-09-09 23:19 UTCGHSA enrichment
  22. 2026-09-08 22:01 UTCEPSS rescore
  23. 2026-09-08 20:13 UTCGHSA enrichment
  24. 2026-09-08 16:16 UTCEG score recompute
  25. 2026-09-08 16:15 UTCGHSA enrichment
  26. 2026-09-07 14:15 UTCEG score recompute
  27. 2026-09-07 14:15 UTCGHSA enrichment
  28. 2026-09-06 13:24 UTCEG score recompute
  29. 2026-09-06 12:44 UTCEG score recompute
  30. 2026-09-06 12:44 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-86258?
CVE-2026-86258 is a medium vulnerability published on September 6, 2026. nbviewer through 1.0.1 contains a path traversal vulnerability in LocalFileHandler.can_show() that uses string-prefix comparison instead of proper path validation. Attackers can read files from sibling directories outside the configured root by requesting paths that share the root as a textual…
When was CVE-2026-86258 disclosed?
CVE-2026-86258 was first published in the National Vulnerability Database on September 6, 2026, with the most recent update on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-86258 actively exploited?
CVE-2026-86258 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 58.2% of all scored CVEs.
What is the CVSS score of CVE-2026-86258?
CVE-2026-86258 has a CVSS v4.0 base score of 5.9 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-86258?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-86258, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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