CVE-2022-23634 in Puma
Summary
by MITRE • 02/12/2022
Puma is a Ruby/Rack web server built for parallelism. Prior to `puma` version `5.6.2`, `puma` may not always call `close` on the response body. Rails, prior to version `7.0.2.2`, depended on the response body being closed in order for its `CurrentAttributes` implementation to work correctly. The combination of these two behaviors (Puma not closing the body + Rails' Executor implementation) causes information leakage. This problem is fixed in Puma versions 5.6.2 and 4.3.11. This problem is fixed in Rails versions 7.02.2, 6.1.4.6, 6.0.4.6, and 5.2.6.2. Upgrading to a patched Rails _or_ Puma version fixes the vulnerability.
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Analysis
by VulDB Data Team • 08/16/2025
CVE-2022-23634 represents a critical information leakage vulnerability affecting the Puma web server and Ruby on Rails framework ecosystem. This vulnerability stems from a fundamental flaw in how Puma handles response body closure within its parallel processing architecture, creating a cascade of issues that compromise application security. The vulnerability manifests when Puma versions prior to 5.6.2 fail to consistently invoke the close method on response bodies, which directly impacts Rails applications that rely on proper resource cleanup for their operational integrity.
The technical root cause of this vulnerability lies in the improper resource management within Puma's response handling mechanism, specifically when dealing with concurrent request processing. When Puma does not call close on response bodies, it creates a scenario where underlying resources remain open and accessible beyond their intended lifecycle. This behavior becomes particularly problematic in Rails applications that utilize the Executor pattern, which depends on proper cleanup of response bodies to maintain accurate state tracking. The vulnerability operates under CWE-404, which classifies improper resource management, and aligns with ATT&CK technique T1531 for credential dumping through resource manipulation.
The operational impact of this vulnerability extends beyond simple resource leakage to create potential information disclosure risks that could compromise application security. When Rails applications depend on CurrentAttributes for maintaining thread-safe state information, the failure to properly close response bodies causes the Executor implementation to malfunction. This malfunction results in state contamination where sensitive information from one request could potentially leak into subsequent requests, particularly in high-concurrency environments where Puma's parallel processing capabilities are fully utilized. The vulnerability affects applications running on affected versions of both Puma and Rails, creating a complex attack surface that requires coordinated patching across both components.
The remediation strategy for CVE-2022-23634 requires immediate action to upgrade either the Puma web server or Rails framework to patched versions. Organizations must upgrade Puma to version 5.6.2 or 4.3.11, while simultaneously ensuring Rails applications are updated to versions 7.0.2.2, 6.1.4.6, 6.0.4.6, or 5.2.6.2. This dual-component approach addresses the vulnerability comprehensively since the issue stems from the interaction between both systems rather than a single point of failure. Security teams should implement comprehensive testing procedures to verify that the patched versions function correctly in their specific environments, particularly focusing on concurrent request handling and resource cleanup behaviors. The vulnerability highlights the importance of proper resource management in web server implementations and demonstrates how seemingly minor flaws in resource handling can create significant security implications in complex application architectures.