CWE-402 Class Draft

Transmission of Private Resources into a New Sphere ('Resource Leak')

This vulnerability occurs when an application unintentionally exposes internal resources, like files, memory, or database connections, to unauthorized users or systems. Essentially, it's a type of…

Definition

What is CWE-402?

This vulnerability occurs when an application unintentionally exposes internal resources, like files, memory, or database connections, to unauthorized users or systems. Essentially, it's a type of resource leak where sensitive assets cross a security boundary.
At its core, this weakness is about a failure in access control for non-data resources. While similar to information exposure (CWE-200), the focus here is on the unauthorized transfer of the resource *itself*—such as a file handle, a socket, or a memory block—into a context where an untrusted actor can use, modify, or exhaust it. This often happens due to logic errors, incorrect cleanup routines, or flawed object lifecycle management, allowing attackers to drain system availability or gain unintended access. For developers, the primary risk is a degradation of system stability and security through resource exhaustion (like Denial of Service) or privilege escalation. To prevent it, rigorously enforce the principle of least privilege for all resource handles, implement robust and audited cleanup paths (finally blocks, using statements, or RAII patterns), and validate that all resource transfers are explicitly authorized. Treat internal handles with the same caution as sensitive data.
Real-world impact

Real-world CVEs caused by CWE-402

  • CVE-2003-0740

    Server leaks a privileged file descriptor, allowing the server to be hijacked.

  • CVE-2004-1033

    File descriptor leak allows read of restricted files.

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-402

  • 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-402

Automated Static Analysis High

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-fix

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Frequently asked questions

Frequently asked questions

What is CWE-402?

This vulnerability occurs when an application unintentionally exposes internal resources, like files, memory, or database connections, to unauthorized users or systems. Essentially, it's a type of resource leak where sensitive assets cross a security boundary.

How serious is CWE-402?

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-402?

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

How can I prevent CWE-402?

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-402?

Plexicus's SAST engine matches the data-flow signature for CWE-402 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-402?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/402.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-402

CWE-668 Parent

Exposure of Resource to Wrong Sphere

This vulnerability occurs when an application unintentionally makes a resource accessible to users or systems that should not have…

CWE-1189 Sibling

Improper Isolation of Shared Resources on System-on-a-Chip (SoC)

This vulnerability occurs when a System-on-a-Chip (SoC) fails to properly separate shared hardware resources between secure (trusted) and…

CWE-1282 Sibling

Assumed-Immutable Data is Stored in Writable Memory

This vulnerability occurs when data that should be permanent and unchangeable—like a bootloader, device IDs, or one-time configuration…

CWE-1327 Sibling

Binding to an Unrestricted IP Address

This vulnerability occurs when software or a service is configured to bind to the IP address 0.0.0.0 (or :: in IPv6), which acts as a…

CWE-1331 Sibling

Improper Isolation of Shared Resources in Network On Chip (NoC)

This vulnerability occurs when a Network on Chip (NoC) fails to properly separate its internal, shared resources—like buffers, switches,…

CWE-134 Sibling

Use of Externally-Controlled Format String

This vulnerability occurs when a program uses a format string from an untrusted, external source (like user input, a network packet, or a…

CWE-200 Sibling

Exposure of Sensitive Information to an Unauthorized Actor

This weakness occurs when an application unintentionally reveals sensitive data to someone who shouldn't have access to it.

CWE-374 Sibling

Passing Mutable Objects to an Untrusted Method

This vulnerability occurs when a function receives a direct reference to mutable data, such as an object or array, instead of a safe copy…

CWE-375 Sibling

Returning a Mutable Object to an Untrusted Caller

This vulnerability occurs when a method directly returns a reference to its internal mutable data, allowing untrusted calling code to…

Resources

Further reading

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