CVE-2026-39987
Confirmed PUBLISHEDmarimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass
1 day faster than CISA KEV
Recommended Action
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
At a Glance
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.
- CVE Published
- Apr 09, 2026
- Exploitation Reported
- Jun 01, 2026
- CVSS
- 9.3 Critical
- EPSS
- 95.6%
Affected Versions
| Vendor | Product | Version | Status |
|---|---|---|---|
| marimo-team |
marimo
|
< 0.23.0 |
Affected |
CVE References
- https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xc github.com · CVE Record https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6...
- https://github.com/marimo-team/marimo/pull/9098 github.com · CVE Record https://github.com/marimo-team/marimo/pull/9098
- https://github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6c60d1d7c68cfd12a github.com · CVE Record https://github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6...
Recommended Actions
- Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
- Check enrichment artifacts for scanner coverage and available PoCs before rolling remediation validation.
- Use the Pro API to automate enrichment, telemetry, and workflow delivery for VM, SOC, and CTI pipelines.
Known Exploited Vulnerability Sources
Catalogues that list this CVE as a known exploited vulnerability.
Per-source evidence links for KEV attestations are available through the KEVIntel Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CVE First | 2026-06-01 13:23 UTC |
| CISA | 2026-06-02 14:01 UTC |
Scanner Artifacts
Nuclei and Metasploit references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/javascript/cves/2026/CVE-2026-39987.yaml | Jun 01, 2026 |
Virtual Patch
Compensating WAF rules to help reduce exposure to this CVE. Rule content and deployable vendor exports are available with KEVIntel Enterprise.
KEVIntel does not currently have a virtual patch for this CVE. When available, KEVIntel virtual patches ship as deployable ModSecurity, Cloudflare, and AWS WAF rules.
Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to KEVIntel Enterprise users.
CVSS Scores
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
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploitation Status
Exploited in the wild
Recorded 2026-06-01 13:23:39 UTC · CVE
Proof of concept available
Recorded 2026-06-02 08:37:09 UTC · GitHub
Weaknesses (CWE)
-
Missing Authentication for Critical Function
Scanner Integrations
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/javascript/cves/2026/CVE-2026-39987.yaml | Jun 01, 2026 |
Recent Mentions
DarkWebInformer · May 29, 2026
CVE-2026-39987 is a critical pre-authentication remote code execution flaw in Marimo, a popular open-source reactive Python notebook framework and a modern alternative to Jupyter with roughly 19.6k GitHub stars.
TheHackerNews · May 29, 2026
An unknown threat actor has been observed using a large language model (LLM) agent to conduct post-compromise actions after obtaining initial access following the exploitation of a publicly-accessible Marimo network using a recently disclosed vulnerability. "The attacker compromised an internet-reachable Marimo notebook via CVE-2026-39987, extracted two cloud credentials from the compromised
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
github · Created 2026-06-02 08:37:09 UTC · 0 stars
github · Created 2026-05-24 18:00:33 UTC · 1 stars
CVE-2026-39987 Exploitation Tool - Marimo < 0.23.0 Pre-Auth RCE (WebSocket)
nuclei · Created Unknown
Timeline
Key exploitation, disclosure, scanner coverage, and KEV attestation events for this CVE.
-
14:01 UTC about 2 months ago14:01 UTC · about 2 months ago
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
15:34 UTC about 2 months ago15:34 UTC · about 2 months ago
Nuclei template available
Scanner coverage available
-
13:23 UTC about 2 months ago13:23 UTC · about 2 months ago
Added to KEVIntel KEV Feed
High-confidence, third-party attested exploitation
-
18:00 UTC about 2 months ago18:00 UTC · about 2 months ago
Public PoC available
Public proof-of-concept code published
-
17:16 UTC 3 months ago17:16 UTC · 3 months ago
CVE published
Vulnerability disclosed publicly
-
00:01 UTC 4 months ago00:01 UTC · 4 months ago
CVE ID reserved
Identifier reserved by the CNA
Automate This Intelligence with the Pro API
Confidence scoring, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
Pro API Example
GET /api/v2/pro/kevs/CVE-2026-39987
{
"cve_id": "CVE-2026-39987",
"title": "marimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Auth...",
"affected_vendor": "marimo-team",
"affected_product": "marimo",
"affected_versions": [
{ "vendor": "...", "product": "...", "status": "affected", "display_label": "..." }
],
"confidence": "Confirmed",
"cvss_score": 9.3,
"epss_score": 0.95645,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "...": "Pro API fields" },
"proof_of_concepts": [ "..." ],
"scanner_integrations": [ "..." ]
}