CVE-2026-39987

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2026-04-23), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 9.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, nvd
Exploited in the wild
9.8
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS: 96%CVSS: 9.8Exploit: NoneExposed: 0

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

marimo is a reactive Python notebook. Prior to 0.23.0, Marimo has a Pre-Auth RCE vulnerability. The terminal WebSocket endpoint /terminal/ws lacks authentication validation, allowing an unauthenticated attacker to obtain a full PTY shell and execute arbitrary system commands. Unlike other WebSocket endpoints (e.g., /ws) that correctly call validate_auth() for authentication, the /terminal/ws endpoint only checks the running mode and platform support before accepting connections, completely skipping authentication verification. This vulnerability is fixed in 0.23.0.

CVSS v3
9.8
EG Score
9.8(high)
EG Risk
99(Act)
EG Risk 99/100SSVC: Act

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
Severity98% × 45%
Exploitation100% × 40%
Automatability100% × 15%
Action: Fix now — active exploitation, automatable, high impact.
EPSS
99.9%
KEV
⚠ Exploited

Published

April 9, 2026

Last Modified

April 23, 2026

Advisory Details (5)

Auto-updated May 11, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: github, cisa.
generic🔴 Active Exploitation

Marimo OSS Python Notebook RCE: From Disclosure to Exploitation in Under 10 Hours | Sysdig

https://www.sysdig.com/blog/marimo-oss-python-notebook-rce-from-disclosure-to-exploitation-in-under-10-hours
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-39987
github Patch Available🟡 PoC Available

Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass · Advisory · marimo-team/marimo · GitHub

https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xc
generic

fix: properly authenticate terminal route by mscolnick · Pull Request #9098 · marimo-team/marimo · GitHub

https://github.com/marimo-team/marimo/pull/9098
generic

fix: properly authenticate terminal route (#9098) · marimo-team/marimo@c24d480 · GitHub

https://github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6c60d1d7c68cfd12a

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
marimo0.0.0 ... 0.9.9 (370 versions)0.23.0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 5× in last 7d / 22× 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. 2026-07-23 03:10 UTCEG score recompute
  2. 2026-07-23 00:04 UTCEG score recompute
  3. 2026-07-22 19:40 UTCCISA KEV update
  4. 2026-07-21 14:37 UTCCISA KEV update
  5. 2026-07-17 10:30 UTCEG score recompute
  6. 2026-07-16 17:04 UTCCISA KEV update
  7. 2026-07-15 16:49 UTCCISA KEV update
  8. 2026-07-15 15:04 UTCCISA KEV update
  9. 2026-07-15 02:00 UTCEPSS rescore
  10. 2026-07-14 18:05 UTCCISA KEV update
  11. 2026-07-13 17:07 UTCCISA KEV update
  12. 2026-07-10 17:52 UTCCISA KEV update
  13. 2026-07-07 19:01 UTCCISA KEV update
  14. 2026-07-07 17:16 UTCCISA KEV update
  15. 2026-07-01 19:16 UTCCISA KEV update
  16. 2026-07-01 15:06 UTCEPSS rescore
  17. 2026-06-30 23:22 UTCEPSS rescore
  18. 2026-06-29 19:12 UTCCISA KEV update
  19. 2026-06-25 19:15 UTCCISA KEV update
  20. 2026-06-25 13:49 UTCEPSS rescore
  21. 2026-06-25 13:49 UTCEPSS rescore
  22. 2026-06-23 21:33 UTCEPSS rescore
  23. 2026-06-23 17:44 UTCCISA KEV update
  24. 2026-06-18 16:13 UTCCISA KEV update
  25. 2026-06-17 17:53 UTCEPSS rescore
Show 53 more
  1. 2026-06-16 19:33 UTCCISA KEV update
  2. 2026-06-15 19:33 UTCCISA KEV update
  3. 2026-06-15 17:49 UTCEPSS rescore
  4. 2026-06-14 23:18 UTCEPSS rescore
  5. 2026-06-12 23:12 UTCEPSS rescore
  6. 2026-06-12 23:12 UTCEPSS rescore
  7. 2026-06-12 17:35 UTCCISA KEV update
  8. 2026-06-11 19:10 UTCCISA KEV update
  9. 2026-06-10 22:18 UTCEPSS rescore
  10. 2026-06-09 18:42 UTCCISA KEV update
  11. 2026-06-09 17:12 UTCCISA KEV update
  12. 2026-06-08 19:16 UTCCISA KEV update
  13. 2026-06-08 17:26 UTCCISA KEV update
  14. 2026-06-08 14:17 UTCEPSS rescore
  15. 2026-06-08 14:17 UTCEPSS rescore
  16. 2026-06-07 15:25 UTCEPSS rescore
  17. 2026-06-07 15:25 UTCEPSS rescore
  18. 2026-06-07 15:25 UTCEPSS rescore
  19. 2026-06-06 13:47 UTCEPSS rescore
  20. 2026-06-06 13:47 UTCEPSS rescore
  21. 2026-06-05 22:47 UTCEPSS rescore
  22. 2026-06-05 22:47 UTCEPSS rescore
  23. 2026-06-05 22:43 UTCCISA KEV update
  24. 2026-06-05 06:10 UTCEPSS rescore
  25. 2026-06-05 06:10 UTCEPSS rescore
  26. 2026-06-04 13:12 UTCEPSS rescore
  27. 2026-06-04 13:12 UTCEPSS rescore
  28. 2026-06-03 19:09 UTCCISA KEV update
  29. 2026-06-02 20:13 UTCEPSS rescore
  30. 2026-06-02 18:32 UTCCISA KEV update
  31. 2026-06-01 20:42 UTCCISA KEV update
  32. 2026-05-31 00:16 UTCEPSS rescore
  33. 2026-05-31 00:16 UTCEPSS rescore
  34. 2026-05-31 00:16 UTCEPSS rescore
  35. 2026-05-29 22:20 UTCCISA KEV update
  36. 2026-05-28 13:44 UTCEPSS rescore
  37. 2026-05-28 13:44 UTCEPSS rescore
  38. 2026-05-28 13:44 UTCEPSS rescore
  39. 2026-05-27 20:35 UTCCISA KEV update
  40. 2026-05-27 13:40 UTCEPSS rescore
  41. 2026-05-27 13:40 UTCEPSS rescore
  42. 2026-05-27 13:40 UTCEPSS rescore
  43. 2026-05-26 19:13 UTCCISA KEV update
  44. 2026-05-26 07:18 UTCEPSS rescore
  45. 2026-05-26 07:18 UTCEPSS rescore
  46. 2026-05-22 19:13 UTCCISA KEV update
  47. 2026-05-21 22:36 UTCCISA KEV update
  48. 2026-05-20 22:38 UTCEPSS rescore
  49. 2026-05-20 22:38 UTCEPSS rescore
  50. 2026-05-20 17:33 UTCCISA KEV update
  51. 2026-05-18 21:50 UTCEG score recompute
  52. 2026-05-18 21:22 UTCCISA KEV update
  53. 2026-05-18 21:22 UTCCISA KEV update

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleijavascript/cves/2026/CVE-2026-39987.yaml
    First seen Jan 1, 2026

    Marimo <= 0.20.4 - Pre-Auth Terminal WebSocket RCE

    Open source ↗

Related CVEs(same CWE)

Frequently asked(6)

What is CVE-2026-39987?
CVE-2026-39987 is a critical vulnerability published on April 9, 2026. marimo is a reactive Python notebook. Prior to 0.23.0, Marimo has a Pre-Auth RCE vulnerability. The terminal WebSocket endpoint /terminal/ws lacks authentication validation, allowing an unauthenticated attacker to obtain a full PTY shell and execute arbitrary system commands. Unlike other WebSocket…
When was CVE-2026-39987 disclosed?
CVE-2026-39987 was first published in the National Vulnerability Database on April 9, 2026, with the most recent update on April 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-39987 actively exploited?
Yes. CISA added CVE-2026-39987 to the Known Exploited Vulnerabilities catalog on April 23, 2026, affecting Marimo Marimo. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2026-39987?
CVE-2026-39987 has a CVSS v3 base score of 9.8 (NVD).
Which products are affected by CVE-2026-39987?
CVE-2026-39987 affects Marimo Marimo. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2026-39987?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-39987, 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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