CWE-391: Unchecked Error Condition

Code Examples & CVEs

Demonstrative Examples

The following code excerpt ignores a rarely-thrown exception from doExchange().

If a RareException were to ever be thrown, the program would continue to execute as though nothing unusual had occurred. The program records no evidence indicating the special situation, potentially frustrating any later attempt to explain the program's behavior.

BadJava

try {doExchange();}catch (RareException e) {                                                                                 // this can never happen                                                                           }

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-391 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-391, Unchecked Error Condition, 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 Unchecked Error Condition during Requirements

MITRE associates mitigation with Requirements, and Implementation; documented detection approaches include Automated Static Analysis; recorded impacts include Varies by Context, Unexpected State, and Alter Execution Logic. Use these source-defined anchors to turn CWE-391 into implementation, review, and verification checks for the affected component.

CWE-391: Unchecked Error Condition — MITRE CWE

Triage CWE-391 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-391, Unchecked Error Condition, 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-391

Apply MITRE's full root-cause mapping guidance when using CWE-391, Unchecked Error Condition. 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-391 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-391, Unchecked Error Condition. 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-391: Unchecked Error Condition?+

CWE-391: Unchecked Error Condition is a Common Weakness Enumeration (CWE) entry maintained by MITRE. [PLANNED FOR DEPRECATION. SEE MAINTENANCE NOTES AND CONSIDER CWE-252, CWE-248, OR CWE-1069.] Ignoring exceptions and other error conditions may allow an attacker to induce unexpected behavior unnoticed.

What are the security consequences of Unchecked Error Condition?+

If exploited, CWE-391 (Unchecked Error Condition) it can compromise Integrity and Other, leading to outcomes such as Varies by Context, Unexpected State and Alter Execution Logic.

How do you prevent or mitigate Unchecked Error Condition?+

Recommended mitigations for CWE-391 include: The choice between a language which has named or unnamed exceptions needs to be done. While unnamed exceptions exacerbate the chance of not properly dealing with an exception, named exceptions suffer from the up call version of the weak base class problem. A language can be used which requires, at compile time, to catch all serious exceptions. However, one must make sure to use the most current version of the API as new exceptions could be added. Catch all relevant exceptions. This is the recommended solution. Ensure that all exceptions are handled in such a way that you can be sure of the state of your system at any given moment.

Which programming languages are affected by Unchecked Error Condition?+

CWE-391 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-391 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-391: Unchecked Error Condition

Technical Details

Applicable To

Security Consequences

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Impact

Mitigation Strategies

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Description

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Description

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Detection Methods

Code Examples & CVEs

Demonstrative Examples

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-391 with SSDF evidence

Address Unchecked Error Condition during Requirements

Triage CWE-391 against known exploitation evidence

Apply precise root-cause mapping to CWE-391

Validate CWE-391 with root-cause mapping checks

Frequently Asked Questions

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