CVE-2026-33374 in Grafana
Summary
by MITRE • 10/13/2026
The Prometheus rule conversion API endpoints in Grafana do not limit request body size, allowing authenticated users to trigger unbounded memory allocations that can crash the server through out-of-memory conditions.
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Analysis
by VulDB Data Team • 10/13/2026
Grafana serves as a widely adopted open-source platform for monitoring and observability, frequently integrating with Prometheus to visualize time-series data. Within this ecosystem, specific API endpoints are designed to convert rules from the Prometheus format into Grafana’s native rule structure. These conversion mechanisms involve parsing complex configuration files that define alerting logic, recording rules, and evaluation intervals. The vulnerability identified in these endpoints stems from a lack of input validation regarding the size of the request body submitted by authenticated users. When an attacker submits a significantly oversized payload to these API endpoints, the server attempts to allocate memory proportional to the incoming data without imposing any upper bounds or limits on allocation size.
This absence of rate limiting and size constraints leads directly to unbounded memory consumption. As the application processes the excessively large request body, it continuously allocates heap space to store and parse the input data. Since there is no mechanism to cap this growth, the server’s available memory is rapidly exhausted. This scenario creates a classic denial-of-service condition where the Grafana instance becomes unresponsive or crashes entirely due to an out-of-memory error. The impact is severe for operational environments because it disrupts access to critical dashboards and alerts, effectively rendering the monitoring infrastructure unavailable until the service is restarted or the memory pressure is alleviated through external intervention.
From a technical classification perspective, this vulnerability aligns with CWE-400, which describes uncontrolled resource consumption. The flaw allows an authenticated actor to exhaust system resources, leading to service degradation or failure. In terms of offensive security frameworks such as MITRE ATT&CK, this behavior is consistent with the Resource Hijacking technique (T1496), where adversaries consume excessive amounts of computing resources to disrupt availability. Although authentication is required to exploit this flaw, it remains a significant risk in environments where internal users may have elevated privileges or if credentials are compromised through other vectors such as phishing or credential stuffing attacks.
Mitigation strategies should focus on implementing strict input validation and size limits at the application layer. Developers must enforce maximum payload sizes for all API endpoints that handle file uploads or large data structures, ensuring that requests exceeding a defined threshold are rejected before processing begins. Additionally, integrating web server-level protections such as Nginx’s client_max_body_size directive can provide an additional layer of defense by rejecting oversized HTTP requests at the network edge. Regular security audits and static code analysis should be employed to identify similar patterns in other API endpoints within the Grafana application. For users unable to immediately patch their instances, restricting access to these specific conversion APIs through firewall rules or identity provider restrictions can reduce the attack surface until a permanent fix is deployed.