Automated 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.)
CWE-390 Base Draft
Detection of Error Condition Without Action
This weakness occurs when software successfully identifies an error condition but then fails to take any meaningful action to address it. The error is detected but ignored, leaving the system in an…
Definition
What is CWE-390?
This weakness occurs when software successfully identifies an error condition but then fails to take any meaningful action to address it. The error is detected but ignored, leaving the system in an inconsistent or vulnerable state.
Imagine your code checks for a failed login attempt, a missing file, or a network timeout, but then simply logs the event and continues normal execution as if nothing went wrong. This creates a silent failure where the root problem isn't corrected, and the application might proceed using bad data, null pointers, or unstable connections. The core issue is that detection logic is present, but the crucial response—like rolling back a transaction, showing a user-friendly alert, or falling back to a secure default—is completely missing.
For developers, this often stems from placeholder error handling, such as empty `catch` blocks or generic logging statements that don't trigger remediation. To fix it, every error check must have a defined outcome: terminate the operation safely, retry with limitations, notify the user appropriately, or revert to a known good state. Treating error detection as a separate step from the response action leaves critical security and stability gaps that attackers or unexpected conditions can easily exploit.
Real-world impact
Real-world CVEs caused by CWE-390
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A GPU data center manager detects an error due to a malformed request but does not act on it, leading to memory corruption.
How attackers exploit it
Step-by-step attacker path
- 1
The following example attempts to allocate memory for a character. After the call to malloc, an if statement is used to check whether the malloc function failed.
- 2
The conditional successfully detects a NULL return value from malloc indicating a failure, however it does not do anything to handle the problem. Unhandled errors may have unexpected results and may cause the program to crash or terminate.
- 3
Instead, the if block should contain statements that either attempt to fix the problem or notify the user that an error has occurred and continue processing or perform some cleanup and gracefully terminate the program. The following example notifies the user that the malloc function did not allocate the required memory resources and returns an error code.
- 4
In the following C++ example the method readFile() will read the file whose name is provided in the input parameter and will return the contents of the file in char string. The method calls open() and read() may result in errors if the file does not exist or does not contain any data to read. These errors will be thrown when the is_open() method and good() method indicate errors opening or reading the file. However, these errors are not handled within the catch statement. Catch statements that do not perform any processing will have unexpected results. In this case an empty char string will be returned, and the file will not be properly closed.
- 5
The catch statement should contain statements that either attempt to fix the problem or notify the user that an error has occurred and continue processing or perform some cleanup and gracefully terminate the program. The following C++ example contains two catch statements. The first of these will catch a specific error thrown within the try block, and the second catch statement will catch all other errors from within the catch block. Both catch statements will notify the user that an error has occurred, close the file, and rethrow to the block that called the readFile() method for further handling or possible termination of the program.
Vulnerable code example
Vulnerable C
The following example attempts to allocate memory for a character. After the call to malloc, an if statement is used to check whether the malloc function failed.
foo=malloc(sizeof(char)); //the next line checks to see if malloc failed
if (foo==NULL) {
//We do nothing so we just ignore the error.
} Secure code example
Secure C
Instead, the if block should contain statements that either attempt to fix the problem or notify the user that an error has occurred and continue processing or perform some cleanup and gracefully terminate the program. The following example notifies the user that the malloc function did not allocate the required memory resources and returns an error code.
foo=malloc(sizeof(char)); //the next line checks to see if malloc failed
if (foo==NULL) {
printf("Malloc failed to allocate memory resources");
return -1;
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-390
- Implementation Properly handle each exception. 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.
- Implementation If a function returns an error, it is important to either fix the problem and try again, alert the user that an error has happened and let the program continue, or alert the user and close and cleanup the program.
- Testing Subject the product to extensive testing to discover some of the possible instances of where/how errors or return values are not handled. Consider testing techniques such as ad hoc, equivalence partitioning, robustness and fault tolerance, mutation, and fuzzing.
Detection signals
How to detect CWE-390
Plexicus auto-detects CWE-390 and opens a fix PR in under 60 seconds.
Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.
Frequently asked questions What is CWE-390?
How serious is CWE-390?
What languages or platforms are affected by CWE-390?
How can I prevent CWE-390?
How does Plexicus detect and fix CWE-390?
Where can I learn more about CWE-390?
Frequently asked questions
What is CWE-390?
This weakness occurs when software successfully identifies an error condition but then fails to take any meaningful action to address it. The error is detected but ignored, leaving the system in an inconsistent or vulnerable state.
How serious is CWE-390?
MITRE rates the likelihood of exploit as Medium — exploitation is realistic but typically requires specific conditions.
What languages or platforms are affected by CWE-390?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-390?
Properly handle each exception. 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. If a function returns an error, it is important to either fix the problem and try again, alert the user that an error has happened and let the program continue, or alert the user and close and cleanup the program.
How does Plexicus detect and fix CWE-390?
Plexicus's SAST engine matches the data-flow signature for CWE-390 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-390?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/390.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-390
CWE-755 Parent
Improper Handling of Exceptional Conditions
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CWE-209 Sibling
Generation of Error Message Containing Sensitive Information
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CWE-248 Sibling
Uncaught Exception
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CWE-274 Sibling
Improper Handling of Insufficient Privileges
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CWE-280 Sibling
Improper Handling of Insufficient Permissions or Privileges
This vulnerability occurs when a system fails to properly manage situations where it lacks the necessary permissions to perform an action…
CWE-333 Sibling
Improper Handling of Insufficient Entropy in TRNG
This vulnerability occurs when a system fails to properly manage the limited or unpredictable output rate of a true random number…
CWE-392 Sibling
Missing Report of Error Condition
This vulnerability occurs when a system fails to properly signal that an error has happened. Instead of returning a clear error code,…
CWE-395 Sibling
Use of NullPointerException Catch to Detect NULL Pointer Dereference
Using a try-catch block for NullPointerException as a substitute for proper null checks is an anti-pattern. This approach masks the root…
CWE-396 Sibling
Declaration of Catch for Generic Exception
This weakness occurs when code catches a generic exception type like 'Exception' or 'Throwable', which can hide specific errors and create…
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