Auth bypass in Sim

CVE-2026-3431

On SimStudio version below to 0.5.74, the MongoDB tool endpoints accept arbitrary connection parameters from the caller without authentication or host restrictions. An attacker can leverage these endpoints to connect to any reachable MongoDB instance and perform unauthorized operations including reading, modifying, and deleting data.

Vulnerability class: Broken Access Control

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.006 (47.2th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 47.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-3431: held from 0.004 to 0.006.

EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.003

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-3431?
CVE-2026-3431 is a critical-severity vulnerability in Sim, classified under Missing Authorization. CVSS score: 9.8/10. Published 2026-03-02.
How severe is CVE-2026-3431?
Critical severity. CVSS v3 base score is 9.8 out of 10.