Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-433 Variant Incomplete
Unparsed Raw Web Content Delivery
This vulnerability occurs when a web application stores unprocessed files—like configuration scripts or raw source code—in publicly accessible directories using file extensions the server doesn't…
Definition
What is CWE-433?
This vulnerability occurs when a web application stores unprocessed files—like configuration scripts or raw source code—in publicly accessible directories using file extensions the server doesn't recognize.
Web servers are configured to process certain file types (like .php or .asp) before sending them to users. When you place files with extensions like .inc, .config, .bak, or .old in a web-accessible folder, and the server doesn't have a handler for them, it treats them as plain text. The server then delivers the raw, unprocessed file content directly to anyone who requests it.
This becomes critical when these files contain sensitive information such as database connection strings, API keys, internal comments, or backend logic. Attackers can easily discover and download these files, bypassing any intended security controls. To prevent this, always store supporting code and configuration files outside the web root or use server rules to explicitly block access to non-standard extensions.
Real-world impact
Real-world CVEs caused by CWE-433
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".inc" file stored under web document root and returned unparsed by the server
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".inc" file stored under web document root and returned unparsed by the server
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".inc" file stored under web document root and returned unparsed by the server
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direct request to .pl file leaves it unparsed
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.inc file
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unparsed config.conf file
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Chain: uppercase file extensions causes web server to return script source code instead of executing the script.
How attackers exploit it
Step-by-step attacker path
- 1
The following code uses an include file to store database credentials:
- 2
database.inc
- 3
login.php
- 4
If the server does not have an explicit handler set for .inc files it may send the contents of database.inc to an attacker without pre-processing, if the attacker requests the file directly. This will expose the database name and password.
Vulnerable code example
Vulnerable PHP
database.inc
<?php
$dbName = 'usersDB';
$dbPassword = 'skjdh#67nkjd3$3$';
?> Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} 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-433
- Architecture and Design Perform a type check before interpreting files.
- Architecture and Design Do not store sensitive information in files which may be misinterpreted.
Detection signals
How to detect CWE-433
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-433
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Frequently asked questions What is CWE-433?
How serious is CWE-433?
What languages or platforms are affected by CWE-433?
How can I prevent CWE-433?
How does Plexicus detect and fix CWE-433?
Where can I learn more about CWE-433?
Frequently asked questions
What is CWE-433?
This vulnerability occurs when a web application stores unprocessed files—like configuration scripts or raw source code—in publicly accessible directories using file extensions the server doesn't recognize.
How serious is CWE-433?
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-433?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-433?
Perform a type check before interpreting files. Do not store sensitive information in files which may be misinterpreted.
How does Plexicus detect and fix CWE-433?
Plexicus's SAST engine matches the data-flow signature for CWE-433 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-433?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/433.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.