CWE-183 Base Draft

Permissive List of Allowed Inputs

This vulnerability occurs when an application's security filter uses an allowlist that is too broad, mistakenly permitting dangerous inputs that should have been blocked. The flawed assumption that…

Definition

What is CWE-183?

This vulnerability occurs when an application's security filter uses an allowlist that is too broad, mistakenly permitting dangerous inputs that should have been blocked. The flawed assumption that everything on the list is safe creates a direct path for attackers to exploit the system.
An overly permissive allowlist is like a faulty bouncer at a club's door—it lets in troublemakers because the guest list isn't specific enough. Developers often create these lists to validate data like filenames, URLs, or user roles, but if the criteria are vague (e.g., allowing all files with a '.pdf' extension without checking the actual content), attackers can slip malicious payloads through. This bypasses the primary defense, leading to issues like command injection, path traversal, or cross-site scripting. Preventing this requires strict, context-aware validation rules that go beyond simple pattern matching. You must understand the exact, legitimate data your feature needs and deny everything else by default. Managing this at scale across hundreds of APIs and filters is difficult; an ASPM like Plexicus can help you track and remediate these flawed allowlist policies across your entire application stack, ensuring your validation logic is consistently robust.
Real-world impact

Real-world CVEs caused by CWE-183

  • CVE-2019-12799

    chain: bypass of untrusted deserialization issue (CWE-502) by using an assumed-trusted class (CWE-183)

  • CVE-2019-10458

    sandbox bypass using a method that is on an allowlist

  • CVE-2017-1000095

    sandbox bypass using unsafe methods that are on an allowlist

  • CVE-2019-10458

    CI/CD pipeline feature has unsafe elements in allowlist, allowing bypass of script restrictions

  • CVE-2017-1000095

    Default allowlist includes unsafe methods, allowing bypass of sandbox

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-183

  • 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-183

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

Plexicus auto-detects CWE-183 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-183?

This vulnerability occurs when an application's security filter uses an allowlist that is too broad, mistakenly permitting dangerous inputs that should have been blocked. The flawed assumption that everything on the list is safe creates a direct path for attackers to exploit the system.

How serious is CWE-183?

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-183?

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

How can I prevent CWE-183?

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-183?

Plexicus's SAST engine matches the data-flow signature for CWE-183 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-183?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/183.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-183

CWE-697 Parent

Incorrect Comparison

This weakness occurs when a security-critical decision relies on a flawed comparison between two pieces of data. The incorrect logic can…

CWE-1023 Sibling

Incomplete Comparison with Missing Factors

This weakness occurs when a program compares two items but fails to check all the necessary attributes that define their true…

CWE-1024 Sibling

Comparison of Incompatible Types

This vulnerability occurs when code directly compares two values of fundamentally different data types, which can lead to unreliable or…

CWE-1025 Sibling

Comparison Using Wrong Factors

This weakness occurs when a program compares two items but checks the wrong properties or attributes. This flawed comparison leads to…

CWE-1039 Sibling

Inadequate Detection or Handling of Adversarial Input Perturbations in Automated Recognition Mechanism

This vulnerability occurs when a system uses automated AI or machine learning to classify complex inputs like images, audio, or text, but…

CWE-1077 Sibling

Floating Point Comparison with Incorrect Operator

This vulnerability occurs when code compares two floating-point numbers using direct equality operators (like == or !=) without accounting…

CWE-1254 Sibling

Incorrect Comparison Logic Granularity

This vulnerability occurs when a system compares sensitive data, like passwords or authentication tokens, piece-by-piece instead of as a…

CWE-185 Sibling

Incorrect Regular Expression

This vulnerability occurs when a regular expression is written incorrectly, causing it to match or validate data in unintended and…

CWE-581 Sibling

Object Model Violation: Just One of Equals and Hashcode Defined

This vulnerability occurs when a Java class defines either the equals() method or the hashCode() method, but not both, breaking a…

Resources

Further reading

Ready when you are

Don't Let Security
Weigh You Down.

Stop choosing between AI velocity and security debt. Plexicus is the only platform that runs Vibe Coding Security and ASPM in parallel — one workflow, every codebase.