CWE-692: Incomplete Denylist to Cross-Site Scripting

CompoundDraft

The product uses a denylist-based protection mechanism to defend against XSS attacks, but the denylist is incomplete, allowing XSS variants to succeed.

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Extended Description

While XSS might seem simple to prevent, web browsers vary so widely in how they parse web pages, that a denylist cannot keep track of all the variations. The "XSS Cheat Sheet" [REF-714] contains a large number of attacks that are intended to bypass incomplete denylists.

Technical Details

Structure
Chain
Vulnerability Mapping
DISCOURAGED

Applicable To

Languages
Not Language-Specific
Platforms

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-692 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-692, Incomplete Denylist to Cross-Site Scripting, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Make elimination of CWE-692 a product outcome

Apply CISA's Secure by Design principle of taking ownership of customer security outcomes to CWE-692, Incomplete Denylist to Cross-Site Scripting. Put the weakness in the product threat model and security roadmap, fund class-level design and platform changes, prefer safe defaults and reusable guardrails, and publish measurable progress. Do not transfer the primary burden to customer configuration when the manufacturer can remove or contain the root cause in the product.

Shifting the Balance of Cybersecurity Risk: Secure by Design Software — Cybersecurity and Infrastructure Security Agency

Connect Incomplete Denylist to Cross-Site Scripting to documented attack evidence

Recorded impacts include Execute Unauthorized Code or Commands; the entry maps to CAPEC-120, CAPEC-267, CAPEC-71, and CAPEC-80; observed examples include CVE-2007-5727, CVE-2006-3617, and CVE-2006-4308. Use these source-defined anchors to turn CWE-692 into implementation, review, and verification checks for the affected component.

CWE-692: Incomplete Denylist to Cross-Site Scripting — MITRE CWE

Apply precise root-cause mapping to CWE-692

Apply MITRE's full root-cause mapping guidance when using CWE-692, Incomplete Denylist to Cross-Site Scripting. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-692 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-692, Incomplete Denylist to Cross-Site Scripting. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-692: Incomplete Denylist to Cross-Site Scripting?+

CWE-692: Incomplete Denylist to Cross-Site Scripting is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product uses a denylist-based protection mechanism to defend against XSS attacks, but the denylist is incomplete, allowing XSS variants to succeed. While XSS might seem simple to prevent, web browsers vary so widely in how they parse web pages, that a denylist cannot keep track of all the variations. The "XSS Cheat Sheet" [REF-714] contains a large number of attacks that are intended to bypass incomplete denylists.

What are the security consequences of Incomplete Denylist to Cross-Site Scripting?+

If exploited, CWE-692 (Incomplete Denylist to Cross-Site Scripting) it can compromise Confidentiality, Integrity and Availability, leading to outcomes such as Execute Unauthorized Code or Commands.

Which programming languages are affected by Incomplete Denylist to Cross-Site Scripting?+

CWE-692 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Incomplete Denylist to Cross-Site Scripting?+

MITRE documents real CVEs mapped to CWE-692, including CVE-2007-5727, CVE-2006-3617 and CVE-2006-4308. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-692 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

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