CWE-1322 Base Incomplete

Use of Blocking Code in Single-threaded, Non-blocking Context

This vulnerability occurs when an application designed to be single-threaded and non-blocking, for performance and scalability, inadvertently executes code that can block the entire process. If an…

Definition

What is CWE-1322?

This vulnerability occurs when an application designed to be single-threaded and non-blocking, for performance and scalability, inadvertently executes code that can block the entire process. If an attacker can trigger this blocking code, it can cause the application to freeze, leading to a denial of service.
In modern architectures like Node.js, Python asyncio, or Vert.x, a single-threaded event loop handles many operations efficiently by avoiding the overhead of traditional multi-threading. The core principle is that all tasks must yield control quickly. If any piece of code—such as a complex computation, a synchronous file operation, or a network call that waits indefinitely—blocks this thread, the entire event loop stalls. This halts all other connections and requests, crippling the application's responsiveness. Attackers can exploit this by directly invoking slow operations or manipulating environmental factors (like network timeouts or file system permissions) to force a block. The result is a classic denial of service: the application appears to hang or become unresponsive. To prevent this, developers must audit their code in non-blocking contexts, replacing synchronous calls with their asynchronous counterparts and offloading expensive tasks to worker threads or separate services.
Real-world impact

Real-world CVEs caused by CWE-1322

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-1322

  • Implementation Generally speaking, blocking calls should be replaced with non-blocking alternatives that can be used asynchronously. Expensive computations should be passed off to worker threads, although the correct approach depends on the framework being used.
  • Implementation For expensive computations, consider breaking them up into multiple smaller computations. Refer to the documentation of the framework being used for guidance.
Detection signals

How to detect CWE-1322

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.

Plexicus auto-fix

Plexicus auto-detects CWE-1322 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.

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Frequently asked questions

Frequently asked questions

What is CWE-1322?

This vulnerability occurs when an application designed to be single-threaded and non-blocking, for performance and scalability, inadvertently executes code that can block the entire process. If an attacker can trigger this blocking code, it can cause the application to freeze, leading to a denial of service.

How serious is CWE-1322?

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-1322?

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

How can I prevent CWE-1322?

Generally speaking, blocking calls should be replaced with non-blocking alternatives that can be used asynchronously. Expensive computations should be passed off to worker threads, although the correct approach depends on the framework being used. For expensive computations, consider breaking them up into multiple smaller computations. Refer to the documentation of the framework being used for guidance.

How does Plexicus detect and fix CWE-1322?

Plexicus's SAST engine matches the data-flow signature for CWE-1322 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-1322?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/1322.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-1322

CWE-834 Parent

Excessive Iteration

This vulnerability occurs when a program runs a loop too many times because it lacks proper limits on its iterations.

CWE-674 Sibling

Uncontrolled Recursion

This vulnerability occurs when an application fails to limit how deeply a function can call itself. Without proper controls, this…

CWE-835 Sibling

Loop with Unreachable Exit Condition ('Infinite Loop')

An infinite loop occurs when a program's iteration logic contains an exit condition that can never be satisfied, causing the loop to run…

Resources

Further reading

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