An adversary submits data to a target application which contains nested exponential data expansion to produce excessively large output. Many data format languages allow the definition of macro-like structures that can be used to simplify the creation of complex structures. However, this capability can be abused to create excessive demands on a processor's CPU and memory. A small number of nested expansions can result in an exponential growth in demands on memory.
Description
Attack Execution Flow
3
1
Step 1
Explore[Survey the target] An adversary determines the input data stream that is being processed by a data parser that supports using subsitituion on the victim's side.
Use an automated tool to record all instances of URLs to process requests.
Use a browser to manually explore the website and analyze how the application processes requests.
AI Translation
[Indaga sul target] Un avversario determina il flusso di dati in ingresso che viene elaborato da un parser di dati che supporta l'uso di sostituzioni sul lato vittima.
Utilizza uno strumento automatizzato per registrare tutte le istanze di URL per elaborare le richieste.
Usa un browser per esplorare manualmente il sito web e analizzare come l'applicazione elabora le richieste.
Attack Techniques
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Use an automated tool to record all instances of URLs to process requests.
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Use a browser to manually explore the website and analyze how the application processes requests.IT: Utilizza uno strumento automatizzato per registrare tutte le istanze di URL al fine di elaborare le richieste.
2
Step 2
Experiment[Craft malicious payload] The adversary crafts a malicious message containing nested exponential expansion that completely uses up available server resources. See the 'Example Instances' section for details on how to craft this malicious payload.
AI Translation
[Creazione di payload dannoso] L'attore malevolo crea un messaggio dannoso contenente un'espansione esponenziale annidata che esaurisce completamente le risorse disponibili del server. Consultare la sezione "Esempi di istanze" per i dettagli su come creare questo payload dannoso.
3
Step 3
Exploit[Send the message] Send the malicious crafted message to the target URL.
AI Translation
[Invia il messaggio] Invia il messaggio malevolo appositamente creato all'URL di destinazione.
Mitigations
2
Design: Use Libraries And Templates That Minimize Unfiltered Input. Use Methods That Limit Entity Expansion And Throw Exceptions On Attempted Entity Expansion.
Implementation: For Xml Based Data - Disable Altogether The Use Of Inline Dtd Schemas When Parsing Xml Objects. If A Dtd Must Be Used, Normalize, Filter And Use An Allowlist And Parse With Methods And Routines That Will Detect Entity Expansion From Untrusted Sources.
Consequences
Security Scopes Affected
Availability
Potential Impacts
Resource Consumption
Unreliable Execution
Relationships
Parent CAPECs
Resources Required
1
None: No specialized resources are required to execute this type of attack.