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-369 Base Draft
Divide By Zero
A divide-by-zero error occurs when software attempts to perform a division operation where the denominator is zero.
Definition
What is CWE-369?
A divide-by-zero error occurs when software attempts to perform a division operation where the denominator is zero.
This flaw typically happens when user input, external data, or an unexpected program state introduces a zero value into a calculation where it wasn't anticipated. It's especially common in functions handling physical dimensions—like size, length, or coordinates—or in mathematical routines that don't validate their inputs. Without proper checks, the division triggers a runtime error that can crash the application or create an unstable state.
Proactively preventing this requires validating all inputs and implementing safeguards before any division operation. While SAST tools can flag the dangerous pattern, Plexicus uses AI to analyze the context and suggest the specific guard clauses or error-handling code needed to fix it, turning a generic warning into an actionable fix. Managing these validation points across a large codebase is challenging; an ASPM platform like Plexicus helps track and prioritize these flaws for consistent remediation.
Real-world impact
Real-world CVEs caused by CWE-369
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Invalid size value leads to divide by zero.
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"Empty" content triggers divide by zero.
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Height value of 0 triggers divide by zero.
How attackers exploit it
Step-by-step attacker path
- 1
The following Java example contains a function to compute an average but does not validate that the input value used as the denominator is not zero. This will create an exception for attempting to divide by zero. If this error is not handled by Java exception handling, unexpected results can occur.
- 2
By validating the input value used as the denominator the following code will ensure that a divide by zero error will not cause unexpected results. The following Java code example will validate the input value, output an error message, and throw an exception.
- 3
The following C/C++ example contains a function that divides two numeric values without verifying that the input value used as the denominator is not zero. This will create an error for attempting to divide by zero, if this error is not caught by the error handling capabilities of the language, unexpected results can occur.
- 4
By validating the input value used as the denominator the following code will ensure that a divide by zero error will not cause unexpected results. If the method is called and a zero is passed as the second argument a DivideByZero error will be thrown and should be caught by the calling block with an output message indicating the error.
- 5
The following C# example contains a function that divides two numeric values without verifying that the input value used as the denominator is not zero. This will create an error for attempting to divide by zero, if this error is not caught by the error handling capabilities of the language, unexpected results can occur.
Vulnerable code example
Vulnerable Java
The following Java example contains a function to compute an average but does not validate that the input value used as the denominator is not zero. This will create an exception for attempting to divide by zero. If this error is not handled by Java exception handling, unexpected results can occur.
public int computeAverageResponseTime (int totalTime, int numRequests) {
return totalTime / numRequests;
} Secure code example
Secure Java
By validating the input value used as the denominator the following code will ensure that a divide by zero error will not cause unexpected results. The following Java code example will validate the input value, output an error message, and throw an exception.
public int computeAverageResponseTime (int totalTime, int numRequests) throws ArithmeticException {
if (numRequests == 0) {
System.out.println("Division by zero attempted!");
throw ArithmeticException;
}
return totalTime / numRequests;
} 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-369
- Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
- Implementation Validate input at trust boundaries; use allowlists, not denylists.
- Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
- Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
- Operation Monitor logs for the runtime signals listed in the next section.
Detection signals
How to detect CWE-369
Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.
Plexicus auto-detects CWE-369 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-369?
How serious is CWE-369?
What languages or platforms are affected by CWE-369?
How can I prevent CWE-369?
How does Plexicus detect and fix CWE-369?
Where can I learn more about CWE-369?
Frequently asked questions
What is CWE-369?
A divide-by-zero error occurs when software attempts to perform a division operation where the denominator is zero.
How serious is CWE-369?
MITRE rates the likelihood of exploit as Medium — exploitation is realistic but typically requires specific conditions.
What languages or platforms are affected by CWE-369?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-369?
Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.
How does Plexicus detect and fix CWE-369?
Plexicus's SAST engine matches the data-flow signature for CWE-369 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-369?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/369.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-369
CWE-682 Parent
Incorrect Calculation
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CWE-128 Sibling
Wrap-around Error
A wrap-around error happens when a variable exceeds the maximum value its data type can hold, causing it to unexpectedly reset to a very…
CWE-131 Sibling
Incorrect Calculation of Buffer Size
This vulnerability occurs when a program miscalculates the amount of memory needed for a buffer, potentially leading to a buffer overflow…
CWE-1335 Sibling
Incorrect Bitwise Shift of Integer
This vulnerability occurs when a program attempts to shift an integer's bits by an invalid amount—either a negative number or a value…
CWE-1339 Sibling
Insufficient Precision or Accuracy of a Real Number
This vulnerability occurs when a program uses a data type or algorithm that cannot accurately represent or calculate the fractional part…
CWE-135 Sibling
Incorrect Calculation of Multi-Byte String Length
This vulnerability occurs when software incorrectly measures the length of strings containing multi-byte or wide characters, leading to…
CWE-190 Sibling
Integer Overflow or Wraparound
Integer overflow or wraparound occurs when a calculation produces a numeric result that exceeds the maximum value a variable can hold.…
CWE-191 Sibling
Integer Underflow (Wrap or Wraparound)
Integer underflow occurs when a subtraction operation results in a value smaller than the data type's minimum limit, causing the value to…
CWE-193 Sibling
Off-by-one Error
An off-by-one error occurs when a program incorrectly calculates a boundary, such as a loop counter or array index, by being one unit too…
Resources
Further reading
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