CWE-796: Only Filtering Special Elements Relative to a Marker

VariantIncomplete

The product receives data from an upstream component, but only accounts for special elements positioned relative to a marker (e.g. "at the beginning/end of a string; the second argument"), thereby missing remaining special elements that may exist before sending it to a downstream component.

View on MITRE

Code Examples & CVEs

Demonstrative Examples

The following code takes untrusted input and uses a regular expression to filter a "../" element located at the beginning of the input string. It then appends this result to the /home/user/ directory and attempts to read the file in the final resulting path.

Since the regular expression is only looking for an instance of "../" at the beginning of the string, it only removes the first "../" element. So an input value such as:

BadPerl

my $Username = GetUntrustedInput();$Username =~ s/^\.\.\///;my $filename = "/home/user/" . $Username;ReadAndSendFile($filename);

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Detect imprecise mappings involving CWE-796

Review mappings to CWE-796, Only Filtering Special Elements Relative to a Marker, with MITRE's mapping and navigation criteria. Flag any selection that points to a View or Category, remains at a higher abstraction than the available evidence supports, or ignores relevant parent, child, peer, and alternative entries. Treat those findings as mapping-quality defects, correct them before publication, and retain the comparison trail for repeatable audits.

CWE Mapping and Navigation Guidance — MITRE CWE

Prevent CWE-796 through an SSDF control plan

Use NIST SSDF practices to make prevention of CWE-796, Only Filtering Special Elements Relative to a Marker, an explicit development outcome. Translate the CWE definition into security requirements and design constraints, choose safer implementation patterns and toolchain checks, and define acceptance evidence before release. Feed every confirmed occurrence back into the requirements, design review, and coding rules so the same root cause is removed across the product rather than patched in one location.

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

Triage CWE-796 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-796, Only Filtering Special Elements Relative to a Marker, 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

Use MITRE taxonomy anchors to review Only Filtering Special Elements Relative to a Marker

Recorded impacts include Unexpected State; related weaknesses include CWE-795. Use these source-defined anchors to turn CWE-796 into implementation, review, and verification checks for the affected component.

CWE-796: Only Filtering Special Elements Relative to a Marker — MITRE CWE

Validate CWE-796 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-796, Only Filtering Special Elements Relative to a Marker. 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-796: Only Filtering Special Elements Relative to a Marker?+

CWE-796: Only Filtering Special Elements Relative to a Marker is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product receives data from an upstream component, but only accounts for special elements positioned relative to a marker (e.g. "at the beginning/end of a string; the second argument"), thereby missing remaining special elements that may exist before sending it to a downstream component.

What are the security consequences of Only Filtering Special Elements Relative to a Marker?+

If exploited, CWE-796 (Only Filtering Special Elements Relative to a Marker) it can compromise Integrity, leading to outcomes such as Unexpected State.

Which programming languages are affected by Only Filtering Special Elements Relative to a Marker?+

CWE-796 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-796 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-796: Only Filtering Special Elements Relative to a Marker

Technical Details

Applicable To

Security Consequences

Scope

Impact

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Detection Methods