CVE-2026-72914 in Mastodon
Summary
by MITRE • 08/11/2026
Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1, the administrative statistics endpoints handled by Api::V1::Admin::MeasuresController and Api::V1::Admin::RetentionController checked authorization only after beginning expensive calculations. Anonymous callers could submit keys, start_at, and end_at parameters that caused long-running SQL queries in Admin::Metrics::Measure, Admin::Metrics::Retention, and Admin::Metrics::Dimension::BaseDimension, allowing repeated requests to exhaust server resources. This issue is fixed in versions 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1.
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Analysis
by VulDB Data Team • 08/11/2026
The vulnerability described represents a critical resource exhaustion flaw in Mastodon's administrative statistics endpoints that falls under the category of denial of service through excessive computation. This issue was present across multiple versions of the ActivityPub-based social network server, specifically affecting the Api::V1::Admin::MeasuresController and Api::V1::Admin::RetentionController components. The fundamental problem lies in the improper order of operations where authorization checks are deferred until after expensive computational processes have already begun, creating a pathway for malicious actors to consume system resources without proper authentication.
The technical implementation flaw stems from the controller logic that processes administrative statistics requests by first accepting and validating parameters such as keys, start_at, and end_at before performing any authorization validation. This design pattern creates an opportunity for attackers to submit crafted requests that trigger long-running SQL queries within the Admin::Metrics::Measure, Admin::Metrics::Retention, and Admin::Metrics::Dimension::BaseDimension classes. These components are responsible for calculating various administrative metrics and retention statistics, which inherently require significant database processing power and memory allocation.
From a cybersecurity perspective, this vulnerability aligns with CWE-400, which addresses uncontrolled resource consumption, and represents a classic example of a denial of service attack that exploits inefficient input validation and authorization flow. The operational impact is severe as anonymous users can repeatedly submit requests that cause the server to perform expensive calculations without any authentication barriers, leading to resource exhaustion that affects legitimate administrative functions and potentially impacts overall service availability. This flaw creates a significant risk for system administrators who rely on these endpoints for monitoring and managing their instances.
The attack vector demonstrates how improper access control implementation can lead to substantial operational disruptions in web applications, particularly those handling sensitive administrative data. The fix implemented in versions 4.4.21, 4.5.14, 4.6.4, and 4.7.0-beta.1 addresses this by ensuring that authorization validation occurs before any computationally intensive operations begin, following the principle of early exit and proper input validation. This approach aligns with security best practices outlined in the OWASP Top Ten and adheres to the ATT&CK framework's concept of privilege escalation through resource exhaustion attacks. The remediation effectively prevents unauthorized access to administrative functions while maintaining proper access control boundaries that protect system resources from abuse.
The vulnerability highlights the importance of implementing defense-in-depth strategies in web applications, particularly in administrative interfaces where sensitive operations are performed. The issue demonstrates how seemingly minor implementation details in authorization flow can create substantial security risks, emphasizing the need for rigorous code review processes and security testing methodologies. Organizations running Mastodon instances should prioritize updating to the patched versions to eliminate this potential attack surface that could be exploited by threat actors seeking to disrupt service availability or gain unauthorized access to administrative functions through resource exhaustion techniques.