CWE-76: Improper Neutralization of Equivalent Special Elements

Extended Description

The product may have a fixed list of special characters it believes is complete. However, there may be alternate encodings, or representations that also have the same meaning. For example, the product may filter out a leading slash (/) to prevent absolute path names, but does not account for a tilde (~) followed by a user name, which on some *nix systems could be expanded to an absolute pathname. Alternately, the product might filter a dangerous "-e" command-line switch when calling an external program, but it might not account for "--exec" or other switches that have the same semantics.

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-76 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-76, Improper Neutralization of Equivalent Special Elements, 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

Address Improper Neutralization of Equivalent Special Elements during Requirements

MITRE associates mitigation with Requirements, and Implementation; recorded impacts include Other; related weaknesses include CWE-75. Use these source-defined anchors to turn CWE-76 into implementation, review, and verification checks for the affected component.

CWE-76: Improper Neutralization of Equivalent Special Elements — MITRE CWE

Triage CWE-76 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-76, Improper Neutralization of Equivalent Special Elements, 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-76

Apply MITRE's full root-cause mapping guidance when using CWE-76, Improper Neutralization of Equivalent Special Elements. 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-76 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-76, Improper Neutralization of Equivalent Special Elements. 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-76: Improper Neutralization of Equivalent Special Elements?+

CWE-76: Improper Neutralization of Equivalent Special Elements is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product correctly neutralizes certain special elements, but it improperly neutralizes equivalent special elements. The product may have a fixed list of special characters it believes is complete. However, there may be alternate encodings, or representations that also have the same meaning. For example, the product may filter out a leading slash (/) to prevent absolute path names, but does not account for a tilde (~) followed by a user name, which on some *nix systems could be expanded to an absolute pathname. Alternately, the product might filter a dangerous "-e" command-line switch when calling an external program, but it might not account for "--exec" or other switches that have the same semantics.

What are the security consequences of Improper Neutralization of Equivalent Special Elements?+

If exploited, CWE-76 (Improper Neutralization of Equivalent Special Elements) it can compromise Other, leading to outcomes such as Other.

How do you prevent or mitigate Improper Neutralization of Equivalent Special Elements?+

Recommended mitigations for CWE-76 include: Programming languages and supporting technologies might be chosen which are not subject to these issues. Utilize an appropriate mix of allowlist and denylist parsing to filter equivalent special element syntax from all input.

Which programming languages are affected by Improper Neutralization of Equivalent Special Elements?+

CWE-76 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

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

A CWE (Common Weakness Enumeration) like CWE-76 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-76: Improper Neutralization of Equivalent Special Elements

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