CVE-2026-39987: Marimo Remote Code Execution Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 23 Apr 2026, 14 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 99.6%
EPSS score, percentile 99.9 of all scored records
- How severe?
- 9.3 Critical
CVSS v4.0 base score, given by the CNA
- What should I do?
CISA deadline 7 May 2026. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- < 0.23.0
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA due date for this action: 7 May 2026.
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
- https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xc
- https://nvd.nist.gov/vuln/detail/CVE-2026-39987
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | < 0.23.0 |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
Marimo contains an pre-authorization remote code execution vulnerability, allowing an unauthenticated attacked to shell access and execute arbitrary system commands.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2026-39987 to its Known Exploited Vulnerabilities (KEV) catalog on 23 Apr 2026.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 7 May 2026.
- The CVE record was published on 9 Apr 2026, 14 days before it was added to KEV.
- The CVE record carries a CVSS v4.0 base score of 9.3 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 99.6% (percentile 99.9), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
marimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass
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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-306: Missing Authentication for Critical Function
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 9 Apr 2026 | CVE record published |
| 23 Apr 2026 | Added to CISA KEV |
| 24 Apr 2026 | CVE record last updated |
| 7 May 2026 | CISA due date for the required action |