CWE-650 Variant Incomplete High likelihood

Trusting HTTP Permission Methods on the Server Side

This vulnerability occurs when a server incorrectly assumes that HTTP GET requests are always safe and cannot change server-side data. Attackers can exploit this flawed assumption to bypass security…

Definition

What is CWE-650?

This vulnerability occurs when a server incorrectly assumes that HTTP GET requests are always safe and cannot change server-side data. Attackers can exploit this flawed assumption to bypass security controls and perform unauthorized actions like modifying or deleting resources.
HTTP methods like GET are designed by specification to retrieve information without side effects, leading developers to sometimes rely on them as a security boundary. The problem is that the protocol itself doesn't enforce this; it's entirely up to the application code. Developers can—and often do—program their endpoints to accept GET requests that create, update, or delete data, especially in REST APIs. If access controls are only checked for methods like POST, PUT, or DELETE, attackers can simply use a GET request to perform the same dangerous actions. You must enforce authorization checks based on the user's permissions and the action's intent, not the HTTP method used. Never assume that POST, PUT, or DELETE are the only methods capable of altering state. Your security logic should validate every request, regardless of whether it's a GET or another method, to ensure the user is authorized for the specific operation they are trying to perform.
Real-world impact

Real-world CVEs caused by CWE-650

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-650

  • System Configuration Configure ACLs on the server side to ensure that proper level of access control is defined for each accessible resource representation.
Detection signals

How to detect CWE-650

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-650 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-650?

This vulnerability occurs when a server incorrectly assumes that HTTP GET requests are always safe and cannot change server-side data. Attackers can exploit this flawed assumption to bypass security controls and perform unauthorized actions like modifying or deleting resources.

How serious is CWE-650?

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-650?

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

How can I prevent CWE-650?

Configure ACLs on the server side to ensure that proper level of access control is defined for each accessible resource representation.

How does Plexicus detect and fix CWE-650?

Plexicus's SAST engine matches the data-flow signature for CWE-650 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-650?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/650.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-650

CWE-436 Parent

Interpretation Conflict

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CWE-113 Sibling

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CWE-115 Sibling

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CWE-437 Sibling

Incomplete Model of Endpoint Features

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CWE-444 Sibling

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

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CWE-626 Sibling

Null Byte Interaction Error (Poison Null Byte)

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CWE-86 Sibling

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Resources

Further reading

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