marimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass (CVE-2026-39987) | HOL Guard CVE

High severityKnown ExploitedCVE-2026-39987

marimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass

Answer in brief

CVE-2026-39987 records a High severity vulnerability in marimo Affected by Pre-Auth Remote Code Execution via Terminal WebSocket Authentication Bypass. The current sources mark it as known exploited. The current feed maps marimo-team/marimo (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Apr 9, 2026Updated May 7, 2026Source checked Sep 20, 2026First seen by HOL May 24, 2026Material review May 7, 2026

Upstream Advisory

Key facts

Risk: High
Exploitation: Known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. Known-exploitation status makes exposure review time-sensitive. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps marimo-team/marimo (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
marimo-team/marimogeneric	< 0.23.0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for marimo-team/marimo.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Apr 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
May 7, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
May 24, 2026
Added to CISA KEV
Apr 23, 2026
Evidence: source:kev:kev:kev:record

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.