CWE-464 Base Incomplete High likelihood

Addition of Data Structure Sentinel

This vulnerability occurs when a program unintentionally adds or modifies a special marker, known as a sentinel, within a data structure, leading to critical logic errors.

Definition

What is CWE-464?

This vulnerability occurs when a program unintentionally adds or modifies a special marker, known as a sentinel, within a data structure, leading to critical logic errors.

Data structures often use sentinel values as internal markers to define their boundaries or format. Common examples include the null terminator ('\0') at the end of a string or a special node marking the end of a linked list. These sentinels are control mechanisms for the program itself, not regular data. If an attacker or a logic flaw can inject or alter these markers, the program's fundamental understanding of its own data breaks down. To prevent this, you must rigorously validate all external inputs and implement strict bounds checking to ensure sentinel values are never written into data fields where they don't belong. Treat sentinels as reserved, protected control characters that your data processing logic must explicitly guard against, separating the trusted internal structure of your data from untrusted, user-supplied content.

Real-world impact

Real-world CVEs caused by CWE-464

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 C

The following example assigns some character values to a list of characters and prints them each individually, and then as a string. The third character value is intended to be an integer taken from user input and converted to an int.

Vulnerable C

char *foo;
  foo=malloc(sizeof(char)*5);
  foo[0]='a';
  foo[1]='a';
  foo[2]=fgetc(stdin);
  foo[3]='c';
  foo[4]='\0';
  printf("%c %c %c %c %c \n",foo[0],foo[1],foo[2],foo[3],foo[4]);
  printf("%s\n",foo);

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-464

Implementation / Architecture and Design Encapsulate the user from interacting with data sentinels. Validate user input to verify that sentinels are not present.
Implementation Proper error checking can reduce the risk of inadvertently introducing sentinel values into data. For example, if a parsing function fails or encounters an error, it might return a value that is the same as the sentinel.
Architecture and Design Use an abstraction library to abstract away risky APIs. This is not a complete solution.
Operation Use OS-level preventative functionality. This is not a complete solution.

Detection signals

How to detect CWE-464

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

CWE-464

Don't catalog this weakness. Prove it's reachable.

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Frequently asked questions

What is CWE-464?

This vulnerability occurs when a program unintentionally adds or modifies a special marker, known as a sentinel, within a data structure, leading to critical logic errors.

How serious is CWE-464?

MITRE rates the likelihood of exploit as High — this weakness is actively exploited in the wild and should be prioritized for remediation.

What languages or platforms are affected by CWE-464?

MITRE lists the following affected platforms: C, C++.

How can I prevent CWE-464?

Encapsulate the user from interacting with data sentinels. Validate user input to verify that sentinels are not present. Proper error checking can reduce the risk of inadvertently introducing sentinel values into data. For example, if a parsing function fails or encounters an error, it might return a value that is the same as the sentinel.

How does Plexicus detect and fix CWE-464?

Plexicus's SAST engine matches the data-flow signature for CWE-464 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-464?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/464.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-464

CWE-138 Parent

Addition of Data Structure Sentinel

What is CWE-464?

Real-world CVEs caused by CWE-464

Step-by-step attacker path

Vulnerable C

Secure pseudo

How to prevent CWE-464

How to detect CWE-464

Don't catalog this weakness. Prove it's reachable.

Frequently asked questions

Weaknesses related to CWE-464

Improper Neutralization of Special Elements

Improper Neutralization of Delimiters

Improper Neutralization of Input Terminators

Improper Neutralization of Input Leaders

Improper Neutralization of Quoting Syntax

Improper Neutralization of Escape, Meta, or Control Sequences

Improper Neutralization of Comment Delimiters

Improper Neutralization of Macro Symbols

Improper Neutralization of Substitution Characters

Further reading

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`