Omission of a break statement might be intentional, in order to support fallthrough. Automated detection methods might therefore be erroneous. Semantic understanding of expected product behavior is required to interpret whether the code is correct.
CWE-484 Base Draft
Omitted Break Statement in Switch
This vulnerability occurs when a developer forgets to include a 'break' statement inside a switch-case block. Without it, the code execution 'falls through' and unintentionally runs the logic for…
Definition
What is CWE-484?
This vulnerability occurs when a developer forgets to include a 'break' statement inside a switch-case block. Without it, the code execution 'falls through' and unintentionally runs the logic for subsequent cases, leading to unexpected behavior.
A missing 'break' statement causes a switch block to fail its primary purpose: executing one distinct code path. Instead, it cascades from the matched case into the code for the cases below it. This 'fall-through' behavior is a common logic error that can bypass critical security checks, corrupt data, or trigger functions that should only run under specific conditions.
While some languages allow intentional fall-through for specific patterns, omitting 'break' by mistake is a frequent source of bugs. To prevent this, developers should adopt a defensive coding style, such as always adding a 'break' as the default action and using linter rules to flag missing statements. Explicitly commenting any intentional fall-throughs makes the code safer and more maintainable.
Real-world impact
Real-world CVEs caused by CWE-484
No public CVE references are linked to this CWE in MITRE's catalog yet.
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 4
Iterate until the response leaks data, executes attacker code, or escalates privileges.
Vulnerable code example
Vulnerable Java
In both of these examples, a message is printed based on the month passed into the function:
public void printMessage(int month){
switch (month) {
case 1: print("January");
case 2: print("February");
case 3: print("March");
case 4: print("April");
case 5: print("May");
case 6: print("June");
case 7: print("July");
case 8: print("August");
case 9: print("September");
case 10: print("October");
case 11: print("November");
case 12: print("December");
}
println(" is a great month");
} Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} 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-484
- Implementation Omitting a break statement so that one may fall through is often indistinguishable from an error, and therefore should be avoided. If you need to use fall-through capabilities, make sure that you have clearly documented this within the switch statement, and ensure that you have examined all the logical possibilities.
- Implementation The functionality of omitting a break statement could be clarified with an if statement. This method is much safer.
Detection signals
How to detect CWE-484
Since this weakness is associated with a code construct, it would be indistinguishable from other errors that produce the same behavior.
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.)
Plexicus auto-detects CWE-484 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-484?
How serious is CWE-484?
What languages or platforms are affected by CWE-484?
How can I prevent CWE-484?
How does Plexicus detect and fix CWE-484?
Where can I learn more about CWE-484?
Frequently asked questions
What is CWE-484?
This vulnerability occurs when a developer forgets to include a 'break' statement inside a switch-case block. Without it, the code execution 'falls through' and unintentionally runs the logic for subsequent cases, leading to unexpected behavior.
How serious is CWE-484?
MITRE rates the likelihood of exploit as Medium — exploitation is realistic but typically requires specific conditions.
What languages or platforms are affected by CWE-484?
MITRE lists the following affected platforms: C, C++, Java, C#, PHP.
How can I prevent CWE-484?
Omitting a break statement so that one may fall through is often indistinguishable from an error, and therefore should be avoided. If you need to use fall-through capabilities, make sure that you have clearly documented this within the switch statement, and ensure that you have examined all the logical possibilities. The functionality of omitting a break statement could be clarified with an if statement. This method is much safer.
How does Plexicus detect and fix CWE-484?
Plexicus's SAST engine matches the data-flow signature for CWE-484 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-484?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/484.html. You can also reference OWASP and NIST documentation for adjacent guidance.
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