Security readout for executives and security teams
Plain-English summary
marimo versions before 0.23.0 can let an unauthenticated remote user open a terminal session through the application and run system commands. For exposed notebook servers, this can mean full control of the host account running marimo, data theft, tampering, or service disruption.
Executive priority
Emergency patching is warranted for exposed marimo systems. This is pre-authentication remote code execution with high confidentiality, integrity, and availability impact. Prioritize systems connected to sensitive data, developer credentials, cloud environments, or shared infrastructure.
Technical view
CVE-2026-39987 is a CWE-306 missing authentication issue in marimo’s /terminal/ws WebSocket endpoint. Unlike other WebSocket endpoints that validate authentication, this endpoint accepted connections after mode and platform checks. The CVSS 4.0 score is 9.3. The issue is fixed in marimo 0.23.0.
Likely exposure
Any marimo deployment below 0.23.0 is potentially affected, especially if reachable over a network by untrusted users. The source bundle does not list CPEs, managed-service exposure, or default deployment details, so organizations should inventory installed marimo versions directly.
Exploitation context
The bundle marks CISA KEV as false, so Glexia is not treating this as KEV-confirmed exploitation. However, a cited Sysdig advisory describes exploitation occurring within 10 hours of disclosure, so exposed systems should be handled as actively at risk.
Researcher notes
Focus validation on version exposure and authentication behavior around /terminal/ws. The advisory states /ws used validate_auth(), while /terminal/ws skipped authentication before 0.23.0. Avoid weaponized testing; use controlled checks and logs. No affected CPEs are provided in the bundle.
Mitigation direction
- Upgrade marimo to 0.23.0 or later.
- Prioritize internet-facing and shared marimo notebook servers.
- Restrict network access to marimo until upgraded.
- Review vendor advisory and release notes for any additional guidance.
Validation and detection
- Identify all marimo installations and record versions.
- Confirm no deployment runs marimo below 0.23.0.
- Verify exposed marimo services require authentication for terminal access.
- Review logs for unexpected /terminal/ws activity.
Public sources used
Michael Williams reviewed this cited source version on .
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-306: Credential and account abuse lookup
Authentication and credential weaknesses can make valid-account abuse and credential telemetry useful review starting points. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-39987 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.3 (4.0)
- Known Exploited
- Yes
- Published
Vector: 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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
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——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
9.3CriticalVector: 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
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xcCVE reference · x_refsource_CONFIRM
- https://github.com/marimo-team/marimo/pull/9098CVE reference · x_refsource_MISC
- https://github.com/marimo-team/marimo/commit/c24d4806398f30be6b12acd6c60d1d7c68cfd12aCVE reference · x_refsource_MISC
- https://www.sysdig.com/blog/marimo-oss-python-notebook-rce-from-disclosure-to-exploitation-in-under-10-hoursCVE reference · third-party-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-39987CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Missing Authentication for Critical Function
Missing Authentication for Critical Function represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.