Description

Uncontrolled Resource Consumption (CWE-400) in Elasticsearch can lead denial of service via Excessive Allocation (CAPEC-130)

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.5",
  "pubDate": "2026-09-26T21:16:56.143Z",
  "pubdate": "2026-09-26T21:16:56.143Z",
  "executiveSummary": "This vulnerability pertains to Uncontrolled Resource Consumption (CWE-400) within Elasticsearch, facilitating a Denial of Service (DoS) condition through Excessive Allocation (CAPEC-130).\nThe flaw stems from the application's failure to adequately bound or limit resource consumption when processing specific malformed or oversized requests, allowing an attacker to force the exhaustion of critical system resources such as heap memory or CPU cycles.\nThe primary impact is the degradation or complete cessation of service, rendering the cluster unresponsive to legitimate client queries and administrative operations.\nThis vulnerability affects Elasticsearch instances that lack stringent request validation or resource management policies. An attacker with network access to the cluster can trigger this condition by dispatching crafted payloads designed to maximize resource demand during the parsing or execution phases.\nThe risk implication is significant as it provides a trivial vector for disrupting data availability without requiring elevated privileges. Successful exploitation requires only the ability to interact with the Elasticsearch API endpoints, making it a critical concern for public-facing or multi-tenant environments where request isolation is insufficient.",
  "technicalDetails": "The root cause of this vulnerability is the absence of adequate input validation and resource quotas during the lifecycle of a request within the Elasticsearch engine. When the engine encounters complex or specifically crafted requests, the internal components responsible for query parsing, aggregation, or indexing can trigger excessive allocation of memory buffers or prolonged CPU processing cycles.\nThe exploitation mechanism follows the CAPEC-130 pattern of Excessive Allocation. By providing a payload that forces the underlying Java Virtual Machine (JVM) to allocate large, contiguous blocks of memory or initiate recursive computational loops, an attacker can induce an OutOfMemoryError (OOME) or CPU saturation.\nThe attack flow initiates when an attacker transmits a maliciously crafted HTTP request—such as a deeply nested query, an oversized mapping definition, or an aggregation request with high cardinality—to the Elasticsearch node. Upon arrival, the request enters the request-handling pipeline where the engine attempts to deserialize and process the payload.\nThe vulnerable components include the request parser, the query execution engine, and the memory management sub-systems. Because Elasticsearch relies on the JVM heap for managing request-scoped objects, an unconstrained request can quickly exceed the configured heap size limit. If the cluster is under-provisioned or lacks circuit breakers for specific operations, the resource demand spikes rapidly.\nDuring exploitation, the node becomes unresponsive due to frequent or long-duration Garbage Collection (GC) pauses triggered by memory pressure, or complete process termination if the heap limit is breached. In distributed deployments, if the primary shard is on an affected node, the loss of availability extends to the data partitions managed by that node, potentially inducing a cascading failure across the cluster if requests are load-balanced across multiple nodes susceptible to the same input.\nThe network exposure is typically limited to the interface hosting the Elasticsearch API (often port 9200/TCP). Exploitation does not require authentication unless the cluster is configured with security features (like Elasticsearch Security) that mandate valid credentials. Even in authenticated environments, an attacker with low-level privileges can trigger this vulnerability to impact availability, highlighting the need for robust resource management beyond standard access control."
}