CVE-2026-6658

MEDIUMPre-NVD 5.45.4
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 5.4 from GitHub Security Advisory published 2026-06-26. A secondary CVSS source baseline 5.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 3 sources updated this weekElevated

Also known asEUVD-2026-39642 (ENISA EUVD) · GHSA-9754-6rhw-gj3h (GitHub Security Advisories)Source: ENISA EUVD

5.4EG
EchelonGraph verdictPlan mitigationRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 5.4Exploit: No code on recordExposed services: Not assessed

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

The CVE record's description, written by its CNA (Protect AI (formerly huntr.dev)), states the affected versions: "A vulnerability in jupyter/nbconvert versions <= 7.17.0 allows for Cross-site Scripting (XSS) via unsanitized `text/vnd.mermaid` output in HTML exports." No release containing a fix is confirmed on record.

A vulnerability in jupyter/nbconvert versions <= 7.17.0 allows for Cross-site Scripting (XSS) via unsanitized text/vnd.mermaid output in HTML exports. The data_mermaid block in share/templates/lab/base.html.j2 renders text/vnd.mermaid cell output directly into HTML without escaping, enabling attackers to inject arbitrary HTML/JavaScript by breaking out of the `` tag. This vulnerability impacts any server using nbconvert to render notebooks as HTML, allowing attackers to execute arbitrary JavaScript in the context of users viewing the HTML export.

CVSS v3
5.4
EG Score
5.4MEDIUMmedium confidence
EG Risk
40
EG Risk 40/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity54% × 45%
Impact severity (EG Severity): CVSS 5.4 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.2%
EPSS %ILE
5th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.4): severity, escalated by confirmed exploitation. This CVE's 5.4 is its impact severity (EG Severity), not escalated.

EG Severity
5.4 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.2% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

June 26, 2026

Last Modified

October 25, 2026

Advisory Details (1)

Auto-updated Jun 26, 2026
No fix on record yet.
Web page

huntr - The world's first bug bounty platform for AI/ML

https://huntr.com/bounties/47570290-3b26-4477-8cfa-fdef7db5aefe

Vendor Advisories for CVE-2026-6658(1)

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

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
nbconvert5.6.1-3 ... 7.17.1-2 (21 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
nbconvert6.5.3-3 ... 7.17.1-2 (10 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
nbconvert7.16.6-1, 7.16.6-1+deb13u1, 7.17.0-1, 7.17.1-1, 7.17.1-2
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
nbconvert7.16.6-1, 7.17.0-1, 7.17.1-1, 7.17.1-2
  • every version on: no fix on record
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 40× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 99 of 222 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 123 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  2. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  3. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  4. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  5. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  6. 2026-10-25 22:27 UTCEG score recompute
  7. 2026-10-25 22:27 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  8. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  9. 2026-10-25 14:11 UTCEG score recompute
  10. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  11. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  12. 2026-10-22 19:36 UTCEG score recompute
  13. 2026-10-22 19:36 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  14. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  15. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  16. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  17. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  18. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  19. 2026-10-18 03:20 UTCEG score recompute
  20. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  21. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  22. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  23. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  24. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  25. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.2% · 12th percentile
Show 74 more
  1. 2026-10-12 15:46 UTCEG score recompute
  2. 2026-10-11 19:31 UTCEG score recompute
  3. 2026-10-11 16:46 UTCEG score recompute
  4. 2026-10-11 14:07 UTCEG score recompute
  5. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  6. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  7. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  8. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  9. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  10. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  11. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  12. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  13. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  14. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  15. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  16. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  17. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  18. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  19. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  20. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  21. 2026-09-23 08:19 UTCEG score recompute
  22. 2026-09-23 08:19 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  23. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  24. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  25. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  26. 2026-09-18 07:16 UTCEG score recompute
  27. 2026-09-18 07:16 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  28. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  29. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  30. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  31. 2026-09-14 01:14 UTCEG score recompute
  32. 2026-09-14 01:14 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  33. 2026-09-12 15:40 UTCEG score recompute
  34. 2026-09-12 15:40 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  35. 2026-09-12 15:02 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  36. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  37. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  38. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  39. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  40. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  41. 2026-09-05 15:31 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  42. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  43. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  44. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  45. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  46. 2026-08-30 19:26 UTCEG score recompute
  47. 2026-08-30 19:26 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  48. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  49. 2026-08-28 21:42 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  50. 2026-08-27 23:14 UTCEG score recompute
  51. 2026-08-27 23:14 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  52. 2026-08-26 14:47 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  53. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  54. 2026-08-24 13:04 UTCEG score recompute
  55. 2026-08-24 13:04 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  56. 2026-08-23 10:04 UTCEG score recompute
  57. 2026-08-23 10:04 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  58. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  59. 2026-08-22 09:46 UTCEG score recompute
  60. 2026-08-22 09:46 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  61. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  62. 2026-08-21 07:18 UTCEG score recompute
  63. 2026-08-21 07:18 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  64. 2026-08-20 22:56 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  65. 2026-08-20 06:59 UTCEG score recompute
  66. 2026-08-20 06:59 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  67. 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  68. 2026-08-19 01:04 UTCEG score recompute
  69. 2026-08-19 01:04 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  70. 2026-08-18 13:49 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  71. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.1% · 3rd percentile
  72. 2026-08-17 08:57 UTCEG score recompute
  73. 2026-08-17 08:57 UTCGHSA enrichmentGHSA-9754-6rhw-gj3h · GitHub CVSS 5.4
  74. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.1% · 3rd percentile

Frequently asked(5)

What is CVE-2026-6658?
CVE-2026-6658 is a medium-severity vulnerability; its CVE record was published on June 26, 2026. A vulnerability in jupyter/nbconvert versions <= 7.17.0 allows for Cross-site Scripting (XSS) via unsanitized text/vnd.mermaid output in HTML exports. The data_mermaid block in share/templates/lab/base.html.j2 renders text/vnd.mermaid cell output directly into HTML without escaping, enabling…
When was the CVE record for CVE-2026-6658 published?
The CVE record for CVE-2026-6658 was published on June 26, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 25, 2026; the record at its source may have been updated since.
Is CVE-2026-6658 actively exploited?
CVE-2026-6658 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (5th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-6658?
CVE-2026-6658 has a CVSS base score of 5.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-6658?
No fix for CVE-2026-6658 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The CVE record's description, written by its CNA (Protect AI (formerly huntr.dev)), states the affected versions: "A vulnerability in jupyter/nbconvert versions <= 7.17.0 allows for Cross-site Scripting (XSS) via unsanitized `text/vnd.mermaid` output in HTML exports." No release containing a fix is confirmed on record. The vendor advisories EchelonGraph has for CVE-2026-6658 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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