CVE-2026-42334: Mongoose's Improper Sanitization of $nor in sanitizeFilter May Allow NoSQL Injection

This vulnerability allows bypassing Mongoose’s sanitizeFilter query sanitization mechanism via the $nor operator.

When sanitizeFilter is enabled, Mongoose wraps query operators in $eq to neutralize them. However, prior to the fix, $nor was not included in the set of logical operators that are recursively sanitized. Because $nor accepts an array (like $and and $or), and arrays do not trigger hasDollarKeys(), malicious operators such as $ne, $gt, or $regex could be injected inside a $nor clause without being sanitized.

This may lead to:

• Authentication bypass
• Unauthorized data access
• Data exfiltration

Affected users:

Applications that:

• Explicitly enable sanitizeFilter
• Pass unsanitized user-controlled input directly into query methods (e.g., Model.findOne(req.body)) and rely on sanitizeFilter to strip out query selectors

Applications that validate input schemas, whitelist fields, or avoid passing raw request bodies into queries are not affected. For example, Model.findOne({ user: req.body.user, pwd: req.body.pwd }) is not affected.