Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-453 Variant Draft
Insecure Default Variable Initialization
This vulnerability occurs when software sets an internal variable to an insecure or unnecessarily weak default value during initialization, rather than using the most secure option available.
Definition
What is CWE-453?
This vulnerability occurs when software sets an internal variable to an insecure or unnecessarily weak default value during initialization, rather than using the most secure option available.
Insecure default initialization happens when a developer or framework assigns a starting value to a variable that is inherently vulnerable. Common examples include enabling debug modes, using weak cryptographic keys, granting excessive permissions, or turning security features off by default. This creates a hidden security gap because the system starts in a weakened state, often without the administrator or end-user being aware that they need to change a setting to be secure.
To prevent this, developers should adopt a 'secure by default' design principle. This means the initial configuration should be the most restrictive and safest possible, requiring explicit action to loosen security, not the other way around. Always validate that security-critical variables like encryption settings, authentication flags, and privilege levels are initialized to their strongest values, and ensure documentation clearly warns against using insecure defaults.
Real-world impact
Real-world CVEs caused by CWE-453
-
insecure default variable initialization in BIOS firmware for a hardware board allows DoS
How attackers exploit it
Step-by-step attacker path
- 1
This code attempts to login a user using credentials from a POST request:
- 2
Because the $authorized variable is never initialized, PHP will automatically set $authorized to any value included in the POST request if register_globals is enabled. An attacker can send a POST request with an unexpected third value 'authorized' set to 'true' and gain authorized status without supplying valid credentials.
- 3
Here is a fixed version:
- 4
This code avoids the issue by initializing the $authorized variable to false and explicitly retrieving the login credentials from the $_POST variable. Regardless, register_globals should never be enabled and is disabled by default in current versions of PHP.
Vulnerable code example
Vulnerable PHP
This code attempts to login a user using credentials from a POST request:
```
// $user and $pass automatically set from POST request*
if (login_user($user,$pass)) {
```
$authorized = true;
}
```
...*
if ($authorized) {
```
generatePage();
} Secure code example
Secure PHP
Here is a fixed version:
$user = $_POST['user'];
$pass = $_POST['pass'];
$authorized = false;
if (login_user($user,$pass)) {
$authorized = true;
}
```
...* What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-453
- System Configuration Disable or change default settings when they can be used to abuse the system. Since those default settings are shipped with the product they are likely to be known by a potential attacker who is familiar with the product. For instance, default credentials should be changed or the associated accounts should be disabled.
Detection signals
How to detect CWE-453
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
CWE-453
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Frequently asked questions What is CWE-453?
How serious is CWE-453?
What languages or platforms are affected by CWE-453?
How can I prevent CWE-453?
How does Plexicus detect and fix CWE-453?
Where can I learn more about CWE-453?
Frequently asked questions
What is CWE-453?
This vulnerability occurs when software sets an internal variable to an insecure or unnecessarily weak default value during initialization, rather than using the most secure option available.
How serious is CWE-453?
MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.
What languages or platforms are affected by CWE-453?
MITRE lists the following affected platforms: PHP.
How can I prevent CWE-453?
Disable or change default settings when they can be used to abuse the system. Since those default settings are shipped with the product they are likely to be known by a potential attacker who is familiar with the product. For instance, default credentials should be changed or the associated accounts should be disabled.
How does Plexicus detect and fix CWE-453?
Plexicus's SAST engine matches the data-flow signature for CWE-453 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-453?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/453.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Ready to validate what matters?
Ready to validate what matters?
Plexicus is Proof-Driven AppSec: validated findings, contextual understanding, and reviewed remediation — anchored in evidence, scoped with you.