CWE-834 Class Incomplete

Excessive Iteration

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

Definition

What is CWE-834?

This vulnerability occurs when a program runs a loop too many times because it lacks proper limits on its iterations.
When an attacker can control or influence the loop's conditions, they can force it to run far more times than intended. This quickly drains system resources like CPU cycles and memory, potentially causing slowdowns, service denial, or crashes. Even a loop that isn't technically infinite can be dangerous if each pass consumes significant resources. For developers, the core issue is trusting unvalidated input to control loop counters or termination logic. To prevent this, always enforce explicit, reasonable upper bounds on all iterative processes, especially those influenced by external data like user input, file contents, or network responses.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-834

  • CVE-2011-1027

    Chain: off-by-one error (CWE-193) leads to infinite loop (CWE-835) using invalid hex-encoded characters.

  • CVE-2006-6499

    Chain: web browser crashes due to infinite loop - "bad looping logic [that relies on] floating point math [CWE-1339] to exit the loop [CWE-835]"

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    In this example a mistake exists in the code where the exit condition contained in flg is never called. This results in the function calling itself over and over again until the stack is exhausted.

  2. 2

    Note that the only difference between the Good and Bad examples is that the recursion flag will change value and cause the recursive call to return.

  3. 3

    For this example, the method isReorderNeeded is part of a bookstore application that determines if a particular book needs to be reordered based on the current inventory count and the rate at which the book is being sold.

  4. 4

    However, the while loop will become an infinite loop if the rateSold input parameter has a value of zero since the inventoryCount will never fall below the minimumCount. In this case the input parameter should be validated to ensure that a value of zero does not cause an infinite loop, as in the following code.

Verwundbares Codebeispiel

Vulnerable C

In this example a mistake exists in the code where the exit condition contained in flg is never called. This results in the function calling itself over and over again until the stack is exhausted.

Verwundbar C 
void do_something_recursive (int flg)
 {

```
   ... // Do some real work here, but the value of flg is unmodified
   if (flg) { do_something_recursive (flg); } // flg is never modified so it is always TRUE - this call will continue until the stack explodes
 }
 int flag = 1; // Set to TRUE
 do_something_recursive (flag);
Sicheres Codebeispiel

Secure C

Note that the only difference between the Good and Bad examples is that the recursion flag will change value and cause the recursive call to return.

Sicher C 
void do_something_recursive (int flg)
 {

```
   ... // Do some real work here
   // Modify value of flg on done condition
   if (flg) { do_something_recursive (flg); } // returns when flg changes to 0
 }
 int flag = 1; // Set to TRUE
 do_something_recursive (flag);
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Präventions-Checkliste

How to prevent CWE-834

  • 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.
Erkennungssignale

How to detect CWE-834

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: ``` Fuzz Tester Framework-based Fuzzer Forced Path 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: ``` Focused Manual Spotcheck - Focused manual analysis of source Manual Source Code Review (not inspections)

Automated Static Analysis - Source Code High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Context-configured Source Code Weakness Analyzer

Architecture or Design Review High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Plexicus Auto-Fix

Plexicus erkennt CWE-834 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

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Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-834?

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

Wie gravierend ist CWE-834?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-834 betroffen?

MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.

Wie kann ich CWE-834 verhindern?

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.

Wie erkennt und behebt Plexicus CWE-834?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-834 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-834?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/834.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-834

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CWE-1281 Sibling

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CWE-362 Sibling

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CWE-430 Sibling

Deployment of Wrong Handler

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CWE-431 Sibling

Missing Handler

This vulnerability occurs when a software component lacks the necessary code to properly handle an error or unexpected event.

CWE-662 Sibling

Improper Synchronization

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CWE-670 Sibling

Always-Incorrect Control Flow Implementation

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CWE-696 Sibling

Incorrect Behavior Order

This weakness occurs when a system executes multiple dependent actions in the wrong sequence, leading to unexpected and potentially…

Ressourcen

Further reading

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