CVE-2026-39987
CriticalExploitedPublic exploitMarimo: Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass
Published Apr 8, 2026 · Updated Aug 12, 2026 · Also known as GHSA-2679-6mx9-h9xc, PYSEC-2026-407
Key Facts
Patch immediately- CVE-2026-39987 is a critical-severity vulnerability (CVSS 9.3 v4) affecting Marimo (Coreweave).
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Apr 9, 2026. Public exploit code is available.
- EPSS estimates a 38% probability of exploitation in the next 30 days.
- Fixed versions are available, including Marimo 0.23.0.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v4
9.3
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS (30-day exploit likelihood)
38%
Higher than 98.5% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2026-39987 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Apr 23, 2026 | May 7, 2026 | Not reported |
| Industry KEV feed | Apr 9, 2026 | May 7, 2026 | Not reported |
| CIRCL KEV | Apr 23, 2026 | May 7, 2026 | Not reported |
| ENISA EUVD | Apr 23, 2026 | n/a | Not reported |
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Affected Products
3 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| MarimoCoreweave | >= < 0.23.0 | 0.23.0 |
Patched Releases
Marimo
0.23.0
Timeline
Publicly disclosed
Apr 8, 2026
Added to Industry KEV feed
Apr 9, 2026
Added to CISA KEV
Apr 23, 2026
Added to CIRCL KEV
Apr 23, 2026
Added to ENISA EUVD
Apr 23, 2026
Last updated
Aug 12, 2026
Weakness Type
- CWE-306 Missing Authentication for Critical Function
References
- advisoryGHSA advisory
- advisoryhttps://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39987.json
- advisoryhttps://nvd.nist.gov/vuln/detail/CVE-2026-39987
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
marimo is a reactive Python notebook.
Affected: Marimo (Coreweave) versions >= < 0.23.0. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Apr 9, 2026.
Yes. It was added on Apr 23, 2026 with a federal remediation due date of May 7, 2026.
Public exploit code is available.
Fixed versions are available, including Marimo 0.23.0.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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