CVE-2026-26931 in Metricbeat
Summary
by MITRE • 03/19/2026
Memory Allocation with Excessive Size Value (CWE-789) in the Prometheus remote_write HTTP handler in Metricbeat can lead Denial of Service via Excessive Allocation (CAPEC-130).
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Analysis
by VulDB Data Team • 03/24/2026
The vulnerability identified as CVE-2026-26931 represents a critical memory allocation flaw within the Prometheus remote_write HTTP handler of Metricbeat, a component of the Elastic Stack used for monitoring and observability. This issue stems from CWE-789, which specifically addresses memory allocation with excessive size values, creating a dangerous condition where malicious actors can manipulate the system's memory management through crafted requests. The vulnerability exists in the HTTP handler responsible for processing remote_write requests, which are commonly used to forward metrics data to Prometheus-compatible systems.
The technical flaw manifests when Metricbeat receives a remote_write HTTP request containing a malformed size parameter that exceeds normal operational bounds. This excessive size value triggers an unintended memory allocation operation that consumes disproportionate system resources. The flaw operates at the application layer within the HTTP request processing pipeline, where input validation fails to properly sanitize or limit the size parameters before memory allocation occurs. Attackers can exploit this by crafting malicious HTTP requests with oversized size values, causing the system to allocate memory blocks that far exceed reasonable expectations for legitimate metric data transmission.
The operational impact of this vulnerability is severe, as it can lead to system-wide denial of service conditions where legitimate operations become impossible due to resource exhaustion. When the excessive memory allocation occurs, it can cause the Metricbeat process to consume all available memory, leading to process termination, system instability, or complete system hangs. This vulnerability particularly affects environments where Metricbeat is configured to accept remote_write requests from untrusted sources or where proper input validation has not been implemented. The attack vector is relatively simple to execute, requiring only the ability to send HTTP requests to the affected endpoint, making it a significant concern for monitoring infrastructure.
Mitigation strategies should focus on implementing robust input validation and size parameter enforcement within the remote_write HTTP handler. Organizations should configure Metricbeat with strict limits on incoming request sizes and implement proper rate limiting to prevent abuse. The implementation should include checks that validate all size parameters against predefined maximum values before any memory allocation occurs. Additionally, deployment configurations should disable remote_write functionality when not required, and network segmentation should be implemented to restrict access to the affected endpoint. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and specifically represents a memory exhaustion attack pattern that can be classified under the broader category of resource exhaustion attacks. System administrators should also consider implementing monitoring and alerting for unusual memory consumption patterns that could indicate exploitation attempts.