CWE-685 Variant Draft

Function Call With Incorrect Number of Arguments

This weakness occurs when a program calls a function, method, or subroutine but provides the wrong number of arguments—either too many or too few. This mismatch can cause the program to behave…

Definition

What is CWE-685?

This weakness occurs when a program calls a function, method, or subroutine but provides the wrong number of arguments—either too many or too few. This mismatch can cause the program to behave unpredictably, access incorrect memory, or crash, creating a security vulnerability.
When a function is called with an incorrect argument count, the underlying system mechanics break down. The calling code and the function have mismatched expectations about how data is arranged on the stack or in registers. This can lead to the function reading invalid values, interpreting data incorrectly (like treating a string as a pointer), or corrupting adjacent memory. The immediate result is often undefined behavior, which can manifest as crashes, data corruption, or unexpected program flow. From a security perspective, this flaw is a gateway for more severe exploits. An attacker might manipulate this mismatch to leak sensitive data from memory, bypass security checks, or execute arbitrary code. It's commonly seen in languages that don't enforce strict type checking at compile-time (like C or C++), in cases of incorrect function pointer usage, or when interfacing with external libraries. Developers must ensure function signatures are always correctly matched, especially when using dynamic linking or callback mechanisms.
Real-world impact

Real-world CVEs caused by CWE-685

No public CVE references are linked to this CWE in MITRE's catalog yet.

How attackers exploit it

Step-by-step attacker path

  1. 1

    Identify a code path that handles untrusted input without validation.

  2. 2

    Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.

  3. 3

    Deliver the payload through a normal request and observe the application's reaction.

  4. 4

    Iterate until the response leaks data, executes attacker code, or escalates privileges.

Vulnerable code example

Vulnerable pseudo

MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.

Vulnerable pseudo 
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}
Secure code example

Secure pseudo

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-685

  • Testing Because this function call often produces incorrect behavior it will usually be detected during testing or normal operation of the product. During testing exercise all possible control paths will typically expose this weakness except in rare cases when the incorrect function call accidentally produces the correct results or if the provided argument type is very similar to the expected argument type.
Detection signals

How to detect CWE-685

Other

While this weakness might be caught by the compiler in some languages, it can occur more frequently in cases in which the called function accepts variable numbers of arguments, such as format strings in C. It also can occur in languages or environments that do not require that functions always be called with the correct number of arguments, such as Perl.

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Frequently asked questions

Frequently asked questions

What is CWE-685?

This weakness occurs when a program calls a function, method, or subroutine but provides the wrong number of arguments—either too many or too few. This mismatch can cause the program to behave unpredictably, access incorrect memory, or crash, creating a security vulnerability.

How serious is CWE-685?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-685?

MITRE lists the following affected platforms: C, Perl.

How can I prevent CWE-685?

Because this function call often produces incorrect behavior it will usually be detected during testing or normal operation of the product. During testing exercise all possible control paths will typically expose this weakness except in rare cases when the incorrect function call accidentally produces the correct results or if the provided argument type is very similar to the expected argument type.

How does Plexicus detect and fix CWE-685?

Plexicus's SAST engine matches the data-flow signature for CWE-685 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-685?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/685.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-685

CWE-628 Parent

Function Call with Incorrectly Specified Arguments

This weakness occurs when a function is called with arguments that are incorrectly specified, causing the function to behave in an…

CWE-683 Sibling

Function Call With Incorrect Order of Arguments

This vulnerability occurs when a program calls a function but supplies the arguments in the wrong order, which can cause unexpected…

CWE-686 Sibling

Function Call With Incorrect Argument Type

This vulnerability occurs when a program calls a function or method but passes an argument of the wrong data type, which can cause…

CWE-687 Sibling

Function Call With Incorrectly Specified Argument Value

This vulnerability occurs when a function is called with an argument that holds an incorrect or unexpected value, leading to unintended…

CWE-688 Sibling

Function Call With Incorrect Variable or Reference as Argument

This vulnerability occurs when a function is called with the wrong variable or reference passed as an argument. This simple coding mistake…

Resources

Further reading

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