Incorrect Behavior Order: Early Validation
This vulnerability occurs when an application validates user input before applying security filters or data normalization. Attackers can exploit this order of operations by submitting specially crafted input that passes the initial validation but becomes malicious after the application's filters or canonicalization processes modify it.
To prevent this flaw, validation logic must always run after data normalization and cleansing steps. Common operations like URL decoding, removing whitespace, or converting character encodings can change the input's structure. If you check for threats before these transformations, you create a window where a harmless-looking payload can be altered into a dangerous command, SQL injection, or path traversal attack after it's already been approved. Think of it as checking a guest's ID before they take off a disguise. The secure approach is to first standardize the input (e.g., decode all entities, resolve paths), then cleanse it, and finally validate the sanitized result against your security rules. This ensures you are evaluating the actual data that will be used by your application's core logic, closing the bypass opportunity.
Impact: Bypass Protection MechanismExecute Unauthorized Code or Commands
An attacker could include dangerous input that bypasses validation protection mechanisms which can be used to launch various attacks including injection attacks, execute arbitrary code or cause other unintended behavior.
Strategy: Input Validation
ID : DX-35
The following code attempts to validate a given input path by checking it against an allowlist and then return the canonical path. In this specific case, the path is considered valid if it starts with the string "/safe_dir/".Code Example:
javaCode Example:
javaID : DX-36
This script creates a subdirectory within a user directory and sets the user as the owner.Code Example:
php//filter out '' because other scripts identify user directories by this prefix*
$dirName = str_replace('','',$dirName);
$newDir = $userDir . $dirName;
mkdir($newDir, 0700);
chown($newDir,$userName);}
- PLOVER