CVE-2020-24391: mongo-express unsafe advanced syntax handling enables code execution

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 18 September 2026. Confidence: medium.

critical priorityCVSS 9.8 with network reachability, no authentication and no user interaction, combined with a very high EPSS probability, makes this an urgent patch target.

What it is

mongo-express before 1.0.0 supports certain advanced syntax but implements it unsafely, allowing crafted input to be evaluated rather than treated as data. The flaw is rated critical (CVSS 9.8) and may overlap CVE-2019-10769, so the exact vulnerable code path is not fully described in this record.

Impact

An unauthenticated remote attacker can achieve full compromise of confidentiality, integrity and availability of the mongo-express instance and the MongoDB data it manages. This can lead to arbitrary code execution or full database takeover.

Attack surface

Reachable over the network via the mongo-express web interface with no authentication and no user interaction required, per the CVSS vector AV:N/AC:L/PR:N/UI:N. The specific endpoint or parameter is not identified in the record.

Exploitation

Not listed in CISA KEV and no public exploit reference is tagged, but EPSS is very high at 0.745 (99.5th percentile), indicating strong likelihood of exploitation activity. The patch commit is public, which lowers the effort to develop an exploit.

What to do

• Upgrade mongo-express to 1.0.0 or later, applying the referenced patch commit.
• If upgrade is not possible, restrict network access to the mongo-express interface to trusted management networks only.
• Enable authentication on mongo-express and place it behind a reverse proxy with strong access controls.
• Run mongo-express with least-privilege MongoDB credentials and isolate it from production database clusters.
• Monitor for the overlapping CVE-2019-10769 and apply any related fixes to the query-parser dependency.

Detection

• Inspect mongo-express and MongoDB logs for requests containing advanced query syntax or unexpected JavaScript-like operators.
• Alert on outbound network connections or process spawns from the mongo-express host that are not part of normal operation.
• Monitor for unusual MongoDB commands or document operations originating from the mongo-express service account.
• Track version banners or package inventories to identify mongo-express instances below 1.0.0.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.