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Report · Exploit-DB RSS FeedAbout CVE-2026-39987Published

Marimo 0.20.4 · RCE

Affects MarimoSource Exploit-DB RSS Feed

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Authoritative record:CVE-2026-39987· Critical 9.3

Exploited in the wild · KEV due 7 May 2026 · public exploit available (Exploit-DB) · 99% EPSS : apply the vendor's fix or mitigations to Marimo now.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 4.0 base score
9.3Critical
How severe the flaw is on the 0–10 CVSS scale.
KEV deadline
 US federal agencies must patch by this date; a sensible deadline for everyone else. Other KEV due dates
EPSS
99.7% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
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

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 9 Apr 2026

  2. Exploited in the wild: evidence found.

    Listed in CISA KEV 14 days after disclosure

  3. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by GitHub, Inc.

    , 41 hours before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. In Threat Radar

    record ingested

    , 34 minutes after disclosure

  4. , 14 days after disclosure

  5. KEV remediation due

    US federal deadline

    , 28 days after disclosure

  6. , 146 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

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 software

ProductAffectedFixed in
npmmarimopkg:npm/marimoOther threatsAffected
  • =0.20.4
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

Marimo version 0.20.4 is associated with a remote code execution (RCE) vulnerability identified as CVE-2026-39987. The available information is limited, with no detailed technical data or patch information provided.

Indicators of compromise

Exploit source code

Exploit code for Marimo 0.20.4 - RCE5,429 characters
Title: Marimo  0.20.4 - RCE 
Date: August 2nd, 2026
Exploit Author: Jason Bernier
Vendor Homepage: https://marimo.io/
Software Link: https://github.com/marimo-team/marimo
Version: <=0.20.4
Tested on: Ubuntu 24.04
CVE: CVE-2026-39987
Advisory:
https://github.com/marimo-team/marimo/security/advisories/GHSA-2679-6mx9-h9xc

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Exploit script for CVE-2026-39987, a pre-authentication Remote Code Execution (RCE) vulnerability in Marimo.
The exploit leverages a WebSocket endpoint to execute arbitrary c…

References

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