Fix it in your stack

Tested fixes for CWE-91 in Flask, Spring Boot and ASP.NET Core: the vulnerable code, the fix, a plausible fix that still fails, and the regression tests.

What MITRE says

The description above is MITRE’s definition of CWE-91 in CWE 4.20, a base-level weakness.

Common consequences MITRE lists

  • Confidentiality, Integrity, Availability: Execute Unauthorized Code or Commands; Read Application Data; Modify Application Data

Closest guides

These guides cover the nearest controls and techniques; use them with the references below.

Related guidance · Guide

Prevent NoSQL, LDAP, XPath and expression-language injection

SQL is not the only query language that receives user input. Stop MongoDB operator injection with type checks and $eq, escape LDAP filter values, pass XPath values as variables, and never evaluate SpEL or OGNL built from request data.

Practice

References

  1. CWE-91 in the MITRE CWE list (version 4.20)

This page is generated from MITRE’s CWE 4.20 catalogue (released 30 April 2026) and lists every guide, fix card and lab here that cites CWE-91.

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