CVE-2026-125117: Prototype Pollution (CVSS 8.2)

Description

Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Prior to 6.13.12, 7.8.13, 8.24.7, and 9.11.4, Mongoose can descend into inherited properties while loading database documents in init(), setting dotted paths in $__set, and merging update documents in utils.mergeClone. Attacker-controlled keys such as toString or valueOf can therefore cause Mongoose to write into shared built-in functions instead of an own property. A crafted document, Mixed path, non-strict document or subdocument, findOneAndReplace() replacement, chained update, or Query.prototype.merge() source can overwrite Object.prototype.toString.call, causing later queries on unrelated models to fail until the process restarts. Separately, when an attacker controls the dotted path passed to doc.set(path, value) for a subdocument configured with strict: false, descent through $__set can reach $__schema and alter shared validators or schema options for later documents. Mongoose already blocks __proto__, constructor, and prototype, so this issue overwrites properties on reachable shared objects rather than adding new properties directly to Object.prototype. This issue is fixed in versions 6.13.12, 7.8.13, 8.24.7, and 9.11.4.

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CVSS v3.1 Score

8.2

HIGH

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

EPSS — Exploit Prediction

0.0058

Probability of exploitation

0.48%

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-1321 CWE-1321

References

Other References

Frequently Asked Questions

What is CVE-2026-125117? +

Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Prior to 6.13.12, 7.8.13, 8.24.7, and 9.11.4, Mongoose can descend into inherited properties while loading database documents in init(), setting dotted paths in $__set, and merging update documents in utils.mergeClone. Attacker-controlled keys such as toString or valueOf can therefore cause Mongoose to write into shared built-in functions instead of an own property. A crafted document, Mixed path, non-strict document or subdocument, findOneAndReplace() replacement, chained update, or Query.prototype.merge() source can overwrite Object.prototype.toString.call, causing later queries on unrelated models to fail until the process restarts. Separately, when an attacker controls the dotted path passed to doc.set(path, value) for a subdocument configured with strict: false, descent through $__set can reach $__schema and alter shared validators or schema options for later documents. Mongoose already blocks __proto__, constructor, and prototype, so this issue overwrites properties on reachable shared objects rather than adding new properties directly to Object.prototype. This issue is fixed in versions 6.13.12, 7.8.13, 8.24.7, and 9.11.4. It has a CVSS v3.1 base score of 8.2 (HIGH).

How severe is CVE-2026-125117? +

CVE-2026-125117 has a CVSS v3.1 score of 8.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0058, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-125117? +

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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