CWE-177 (URL编码处理不恰当(Hex编码)) — Vulnerability Class 9

CWE-177 represents a critical input validation weakness where software fails to correctly process URL-encoded data, often leading to security vulnerabilities. Attackers typically exploit this by crafting malicious payloads that bypass initial filtering mechanisms through double-encoding or partial encoding, allowing them to inject harmful scripts or execute unauthorized commands. This evasion technique tricks the application into treating encoded characters as safe literals until they are processed later in the pipeline. To mitigate this risk, developers must implement robust input validation strategies that decode all incoming data early in the request lifecycle. By normalizing inputs before any security checks, applications can consistently identify and reject malicious patterns. Additionally, employing strict allow-lists for expected characters and utilizing parameterized queries further reduces the attack surface, ensuring that encoded inputs are handled predictably and securely throughout the entire processing chain.