Weakness · High
CWE-470: Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')
What it is
The product uses external input with reflection to select which classes or code to use, but it does not sufficiently prevent the input from selecting improper classes or code.
- Severity (our rating)
- High
- Likelihood of exploit
- Not rated by MITRE
- Introduced during
- Architecture and Design, Implementation
- Exploited in the wild
- 2 known exploited CVEs
In more detail
If the product uses external inputs to determine which class to instantiate or which method to invoke, then an attacker could supply values to select unexpected classes or methods. If this occurs, then the attacker could create control flow paths that were not intended by the developer. These paths could bypass authentication or access control checks, or otherwise cause the product to behave in an unexpected manner. This situation becomes a doomsday scenario if the attacker can upload files into a location that appears on the product's classpath (CWE-427) or add new entries to the product's classpath (CWE-426). Under either of these conditions, the attacker can use reflection to introduce new, malicious behavior into the product.
What an attacker can do
- Execute Unauthorized Code or Commands (Integrity, Confidentiality, Availability, Other)
- Alter Execution Logic (Integrity, Confidentiality, Availability, Other)
- DoS: Crash, Exit, or Restart (Availability, Other)
- Other (Availability, Other)
- Read Application Data (Confidentiality)
How to prevent it
Architecture and Design
- Refactor your code to avoid using reflection.
- Do not use user-controlled inputs to select and load classes or code.
Implementation
- Apply strict input validation by using allowlists or indirect selection to ensure that the user is only selecting allowable classes or code.
How to find it
- Automated Static Analysis. Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Exploited in the wild: 2 CVEs
Vulnerabilities caused by CWE-470 that attackers have used, from CISA's Known Exploited Vulnerabilities catalog, newest first.
H2 Security
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Start freeSource: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.