CWE-153: Improper Neutralization of Substitution Characters

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-153 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-153, Improper Neutralization of Substitution Characters, 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

Apply Input Validation controls for Improper Neutralization of Substitution Characters

MITRE associates mitigation with Implementation; the listed strategies include Input Validation, and Output Encoding; recorded impacts include Unexpected State. Use these source-defined anchors to turn CWE-153 into implementation, review, and verification checks for the affected component.

CWE-153: Improper Neutralization of Substitution Characters — MITRE CWE

Triage CWE-153 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-153, Improper Neutralization of Substitution Characters, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-153

Apply MITRE's full root-cause mapping guidance when using CWE-153, Improper Neutralization of Substitution Characters. 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-153 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-153, Improper Neutralization of Substitution Characters. 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-153: Improper Neutralization of Substitution Characters?+

CWE-153: Improper Neutralization of Substitution Characters is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as substitution characters when they are sent to a downstream component.

What are the security consequences of Improper Neutralization of Substitution Characters?+

If exploited, CWE-153 (Improper Neutralization of Substitution Characters) it can compromise Integrity, leading to outcomes such as Unexpected State.

How do you prevent or mitigate Improper Neutralization of Substitution Characters?+

Recommended mitigations for CWE-153 include: Developers should anticipate that substitution characters will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.

Which programming languages are affected by Improper Neutralization of Substitution Characters?+

CWE-153 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 Improper Neutralization of Substitution Characters?+

MITRE documents real CVEs mapped to CWE-153, including CVE-2002-0770. 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-153 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.

CWE-153: Improper Neutralization of Substitution Characters

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Phase

Description

Detection Methods

Code Examples & CVEs

Observed CVE Examples (1)

CWE Relationships

Parent Weaknesses