Automattic Mongoose up to 6.13.11/7.8.12/8.24.6/9.11.3 Discriminator bulkWrite __t type confusion

Summaryinfo

A vulnerability, which was classified as critical, has been found in Automattic Mongoose up to 6.13.11/7.8.12/8.24.6/9.11.3. Impacted is the function bulkWrite of the component Discriminator Handler. The manipulation of the argument __t leads to type confusion. This vulnerability is uniquely identified as CVE-2026-125116. The attack is possible to be carried out remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Automattic Mongoose up to 6.13.11/7.8.12/8.24.6/9.11.3 and classified as critical. This issue affects the function bulkWrite of the component Discriminator Handler. The manipulation of the argument __t with an unknown input leads to a type confusion vulnerability. Using CWE to declare the problem leads to CWE-843. The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type. Impacted is integrity, and availability. The summary by CVE is:

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 uses attacker-controlled discriminator key values, including the default __t field, to index plain-object registries such as Model.discriminators and schema.discriminators without requiring an own property. Values such as constructor, toString, or hasOwnProperty can therefore resolve to inherited built-in functions instead of a registered discriminator, causing type confusion in model construction, document creation, hydration, query and update casting, embedded discriminators, and populate operations. In the bulkWrite() insertOne path with skipValidation enabled, a constructor value can cause a raw input object to be stored without schema casting or strict filtering, and a stored poisoned document can make every query that hydrates it fail until the document is removed. The weakness reads inherited properties but does not modify Object.prototype and is not prototype pollution. This issue is fixed in versions 6.13.12, 7.8.13, 8.24.7, and 9.11.4.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-125116 since 11/09/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 6.13.12, 7.8.13, 8.24.7 or 9.11.4 eliminates this vulnerability.

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Productinfo

Vendor

• Automattic

Name

• Mongoose

Version

• 6.13.0
• 6.13.1
• 6.13.2
• 6.13.3
• 6.13.4
• 6.13.5
• 6.13.6
• 6.13.7
• 6.13.8
• 6.13.9
• 6.13.10
• 6.13.11
• 7.8.0
• 7.8.1
• 7.8.2
• 7.8.3
• 7.8.4
• 7.8.5
• 7.8.6
• 7.8.7
• 7.8.8
• 7.8.9
• 7.8.10
• 7.8.11
• 7.8.12
• 8.24.0
• 8.24.1
• 8.24.2
• 8.24.3
• 8.24.4
• 8.24.5
• 8.24.6
• 9.11.0
• 9.11.1
• 9.11.2
• 9.11.3

Website

• Product: https://github.com/Automattic/mongoose/

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