Content Security Policy (CSP) Missing or Weak

1. Executive Threat Overview

Content Security Policy (CSP) is an HTTP header that allows site operators to restrict the resources (such as JavaScript, CSS, Images) that the browser is allowed to load for a given page. A missing or weakly configured CSP makes a site highly susceptible to Cross-Site Scripting (XSS) and data injection exploits.

In modern web infrastructure, content security policy (csp) missing or weak represents a critical failure mode in security controls. According to A05:2021 - Security Misconfiguration and documented under CWE-693: Protection Mechanism Failure, applications failing to enforce proper controls at this layer expose their attack surface to automated crawlers, botnets, and skilled penetration testers.

When evaluating target perimeters, threat actors systematically probe for this condition using fingerprinting engines like Nmap, Nuclei, and custom fuzzing scripts. If left unresolved, this weakness can be chained with auxiliary application vulnerabilities to achieve elevated privileges, exfiltrate sensitive data, or bypass downstream security filters.

2. Technical & Business Impact

3. Exploitation Mechanics & Attack Vectors

Threat actors identify and exploit this weakness through the following attack phases:

1. Phase 1 (Reconnaissance): The attacker performs automated reconnaissance against the target domain to identify server headers, software versions, and security configurations.
2. Phase 2 (Exploitation): Utilizing known attack vectors associated with CWE-693: Protection Mechanism Failure, the attacker crafts specific payloads or request patterns to trigger the vulnerability.
3. Phase 3 (Post-Exploitation & Impact): Upon successful validation, the attacker leverages the condition to compromise confidential records, manipulate user sessions, or pivot toward internal services.

4. Production Hardening & Remediation

To eliminate this vulnerability, apply the following hardened configurations to your edge web server or application codebase:

Nginx Web Server Configuration

# Recommended Nginx Hardening Configuration for Content Security Policy (CSP) Missing or Weak:
# Apply strict security directives in the relevant server or location block
# Refer to CWE-693: Protection Mechanism Failure remediation standards.

Apache 2.4 / .htaccess

# Apache 2.4 Configuration for Content Security Policy (CSP) Missing or Weak:
# Configure Apache directives in httpd.conf or .htaccess
# Refer to A05:2021 - Security Misconfiguration guidelines.

Application Code Implementation

Define and send a Content-Security-Policy header. Start with a secure default-src policy and whitelist only trusted origins:

Content-Security-Policy: default-src 'self'; script-src 'self' https://trustedscripts.com; style-src 'self' 'unsafe-inline';

5. Verification & Testing Commands

Run the following terminal command to audit and verify that your production fixes are actively enforced:

curl -sI https://example.com/content

6. Frequently Asked Questions