CVE-2026-9740

Description

A vulnerability in MongoDB Server's BSON validation logic allows an unauthenticated user to crash the mongod process by sending a specially crafted message. The BSON validator's handling of certain nested binary data structures permits uncontrolled mutual recursion between validation functions, where each re-entry resets internal depth tracking.

CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0035

Probability of exploitation

0.26%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-674 CWE-674

Affected Products

Vendor	Product	Versions
mongodb	mongodb	7.0.0 — 7.0.35
mongodb	mongodb	8.0.0 — 8.0.24
mongodb	mongodb	8.2.0 — 8.2.10
mongodb	mongodb	8.3.0 — 8.3.3

References

Advisories & Patches

https://jira.mongodb.org/browse/SERVER-125063

Frequently Asked Questions

What is CVE-2026-9740? +

A vulnerability in MongoDB Server's BSON validation logic allows an unauthenticated user to crash the mongod process by sending a specially crafted message. The BSON validator's handling of certain nested binary data structures permits uncontrolled mutual recursion between validation functions, where each re-entry resets internal depth tracking. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-9740? +

CVE-2026-9740 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0035, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-9740? +

CVE-2026-9740 affects products from mongodb, specifically: mongodb. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-9740? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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