CWE-409 Base Incomplet

Improper Handling of Highly Compressed Data (Data Amplification)

This vulnerability occurs when software fails to safely process highly compressed data, where a small input file can trigger the creation of an extremely large amount of data during decompression,…

Définition

What is CWE-409?

This vulnerability occurs when software fails to safely process highly compressed data, where a small input file can trigger the creation of an extremely large amount of data during decompression, overwhelming system resources.
Often called a 'decompression bomb' or 'zip bomb,' this attack exploits the extreme compression ratios possible with formats like ZIP, XML, or PDF. A malicious actor can craft a tiny, harmless-looking file that, when processed by your application, expands to consume gigabytes of memory or disk space, leading to denial of service, crashes, or performance degradation. To prevent this, developers must implement security controls before decompression. This includes setting strict limits on the compression ratio, checking the uncompressed size from file headers before allocating memory, and using streaming decompression with quotas instead of loading entire outputs into memory at once. Treating all compressed input as untrusted and validating its potential impact is a critical step in secure file handling.
Impact réel

Real-world CVEs caused by CWE-409

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

  1. 1

    Identifier un chemin de code qui traite des entrées non fiables sans validation.

  2. 2

    Élaborer une charge utile qui exploite le comportement non sécurisé — injection, traversal, débordement ou abus de logique.

  3. 3

    Délivrer la charge utile via une requête normale et observer la réaction de l'application.

  4. 4

    Itérer jusqu'à ce que la réponse divulgue des données, exécute le code de l'attaquant ou élève les privilèges.

Exemple de code vulnérable

Vulnerable XML

The DTD and the very brief XML below illustrate what is meant by an XML bomb. The ZERO entity contains one character, the letter A. The choice of entity name ZERO is being used to indicate length equivalent to that exponent on two, that is, the length of ZERO is 2^0. Similarly, ONE refers to ZERO twice, therefore the XML parser will expand ONE to a length of 2, or 2^1. Ultimately, we reach entity THIRTYTWO, which will expand to 2^32 characters in length, or 4 GB, probably consuming far more data than expected.

Vulnérable XML 
<?xml version="1.0"?>
  <!DOCTYPE MaliciousDTD [
  <!ENTITY ZERO "A">
  <!ENTITY ONE "&ZERO;&ZERO;">
  <!ENTITY TWO "&ONE;&ONE;">
  ...
  <!ENTITY THIRTYTWO "&THIRTYONE;&THIRTYONE;">
  ]>
  <data>&THIRTYTWO;</data>
Charge utile de l'attaquant

The DTD and the very brief XML below illustrate what is meant by an XML bomb. The ZERO entity contains one character, the letter A. The choice of entity name ZERO is being used to indicate length equivalent to that exponent on two, that is, the length of ZERO is 2^0. Similarly, ONE refers to ZERO twice, therefore the XML parser will expand ONE to a length of 2, or 2^1. Ultimately, we reach entity THIRTYTWO, which will expand to 2^32 characters in length, or 4 GB, probably consuming far more data than expected.

Charge utile de l'attaquant XML 
<?xml version="1.0"?>
  <!DOCTYPE MaliciousDTD [
  <!ENTITY ZERO "A">
  <!ENTITY ONE "&ZERO;&ZERO;">
  <!ENTITY TWO "&ONE;&ONE;">
  ...
  <!ENTITY THIRTYTWO "&THIRTYONE;&THIRTYONE;">
  ]>
  <data>&THIRTYTWO;</data>
Exemple de code sécurisé

Secure pseudo

Sécurisé 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.
Liste de contrôle de prévention

How to prevent CWE-409

  • 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.
Signaux de détection

How to detect CWE-409

SAST High

Exécuter une analyse statique (SAST) sur le code source à la recherche du motif non sécurisé dans le flux de données.

DAST Moderate

Exécuter des tests de sécurité applicative dynamique (DAST) contre le point de terminaison en ligne.

Runtime Moderate

Surveiller les journaux runtime pour détecter des traces d'exception inhabituelles, des entrées malformées ou des tentatives de contournement d'autorisation.

Code review Moderate

Revue de code : signaler tout nouveau code qui traite les entrées de cette surface sans utiliser les helpers du framework validés.

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-409 et ouvre une PR de correction en moins de 60 secondes.

Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.

Obtenir une démo Essayer Plexicus gratuitement
Questions fréquentes

Frequently asked questions

Qu'est-ce que CWE-409 ?

This vulnerability occurs when software fails to safely process highly compressed data, where a small input file can trigger the creation of an extremely large amount of data during decompression, overwhelming system resources.

Quelle est la gravité de CWE-409 ?

MITRE n'a pas publié de note de probabilité d'exploitation pour cette faiblesse. Traitez-la comme un impact moyen jusqu'à ce que votre modèle de menace prouve le contraire.

Quels langages ou plateformes sont affectés par CWE-409 ?

MITRE n'a pas spécifié les plateformes affectées pour ce CWE — il peut s'appliquer à la plupart des stacks applicatives.

Comment puis-je prévenir CWE-409 ?

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.

Comment Plexicus détecte et corrige CWE-409 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-409 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-409 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/409.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-409

CWE-405 Parent

Asymmetric Resource Consumption (Amplification)

This vulnerability occurs when a system allows an attacker to trigger a disproportionate amount of resource consumption—like CPU, memory,…

CWE-1050 Frère

Excessive Platform Resource Consumption within a Loop

This vulnerability occurs when a loop contains code that repeatedly consumes critical system resources like file handles, database…

CWE-1072 Frère

Data Resource Access without Use of Connection Pooling

This weakness occurs when an application creates a new database connection for every request instead of using a managed connection pool.…

CWE-1073 Frère

Non-SQL Invokable Control Element with Excessive Number of Data Resource Accesses

This weakness occurs when a client-side function or method makes an excessive number of individual data requests through a non-SQL data…

CWE-1084 Frère

Invokable Control Element with Excessive File or Data Access Operations

This weakness occurs when a single function or method performs an excessive number of file or database operations, such as repeated reads,…

CWE-1089 Frère

Large Data Table with Excessive Number of Indices

This weakness occurs when an application uses a database table with a very large number of rows and creates too many indexes on it,…

CWE-1094 Frère

Excessive Index Range Scan for a Data Resource

This weakness occurs when a database query performs an index range scan that can access an unnecessarily large number of rows from a…

CWE-1176 Frère

Inefficient CPU Computation

This weakness occurs when software uses inefficient algorithms or suboptimal CPU operations, performing unnecessary or overly complex…

CWE-406 Frère

Insufficient Control of Network Message Volume (Network Amplification)

This vulnerability occurs when a system fails to properly limit the amount of network traffic it can generate in response to a request,…

Ressources

Further reading

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