CWE-394: Unexpected Status Code or Return Value

What is CWE-394?

CWE-394 is Unexpected Status Code or Return Value. The flaw arises when the product does not properly check when a function or operation returns a value that is legitimate for the function, but is not expected by the product. The database currently holds 3 vulnerabilities mapped to CWE-394 and none of them are in the CISA Known Exploited Vulnerabilities catalog.

OWASP TOP 10:2025 RANK10 — A10:2025 — Mishandling of Exceptional Conditions
Related CVES (365 days)3
AbstractionBase
Likelihood of exploit-

Vulnerabilities mapped to CWE-394

3 vulnerabilities200% increase year over year

No data

No vulnerability data in CISA KEV for CWE-394

Official definition

ByMitre CWE

The product does not properly check when a function or operation returns a value that is legitimate for the function, but is not expected by the product.

Characteristics

Modes of introduction

  • Implementation

Common consequences

ImpactScopeExplanation
Unexpected State, Alter Execution LogicIntegrity, Other-

Detection methods

MethodApproachEffectiveness
Automated Static AnalysisAutomated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)High

Representative vulnerabilities

Below are representative vulnerabilities related to this CWE, prioritized by severity.

Sources (2)
MITRE CWE
CWE Terms of Use

Supporting documents

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