CVE-2022-23641 in Discourse
Summary
by MITRE • 02/16/2022
Discourse is an open source discussion platform. In versions prior to 2.8.1 in the `stable` branch, 2.9.0.beta2 in the `beta` branch, and 2.9.0.beta2 in the `tests-passed` branch, users can trigger a Denial of Service attack by posting a streaming URL. Parsing Oneboxes in the background job trigger an infinite loop, which cause memory leaks. This issue is patched in version 2.8.1 of the `stable` branch, 2.9.0.beta2 of the `beta` branch, and 2.9.0.beta2 of the `tests-passed` branch. As a workaround, disable onebox in admin panel completely or specify allow list of domains that will be oneboxed.
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Analysis
by VulDB Data Team • 02/18/2022
The vulnerability identified as CVE-2022-23641 affects Discourse, an open source discussion platform that serves as a collaborative forum for communities and organizations. This security flaw represents a significant denial of service risk that can be exploited by malicious actors to disrupt platform operations. The vulnerability specifically impacts versions prior to 2.8.1 in the stable branch, 2.9.0.beta2 in the beta branch, and 2.9.0.beta2 in the tests-passed branch, indicating a widespread issue across multiple release channels. The flaw manifests when users submit streaming URLs that trigger background processing through the onebox functionality, creating a critical operational weakness that affects system stability and availability.
The technical implementation of this vulnerability stems from improper handling of onebox parsing within background job processing. When a user posts a streaming URL, the system attempts to parse the content through onebox functionality which is designed to embed external content within discussion threads. However, the parsing mechanism contains a logical flaw that creates an infinite loop during background job execution. This infinite loop results in continuous memory allocation without proper cleanup, leading to progressive memory leaks that can eventually exhaust system resources. The issue falls under CWE-835, which specifically addresses infinite loops that can cause denial of service conditions. The vulnerability demonstrates poor resource management and inadequate input validation in the background processing pipeline, creating a condition where legitimate user content can be weaponized to consume excessive system resources.
The operational impact of CVE-2022-23641 extends beyond simple service disruption to potentially compromise the entire platform availability. Memory leaks caused by the infinite loop can gradually consume system resources until the platform becomes unresponsive or crashes entirely. This type of denial of service attack can be executed with minimal technical expertise, making it particularly dangerous for public-facing discussion platforms that rely on continuous availability. The vulnerability affects the core functionality of content embedding and user-generated content processing, which are fundamental to Discourse's purpose as a discussion platform. Attackers can exploit this weakness to render the platform unusable for legitimate users while maintaining their own access to the system, creating a scenario where the platform becomes inaccessible to the community it serves. The impact aligns with ATT&CK technique T1499.004, which covers network denial of service attacks that consume system resources.
The remediation for this vulnerability requires updating to patched versions of the Discourse platform, specifically 2.8.1 for the stable branch, 2.9.0.beta2 for the beta branch, and 2.9.0.beta2 for the tests-passed branch. Organizations should prioritize applying these updates to maintain system integrity and prevent exploitation. As a temporary mitigation, administrators can disable the onebox functionality entirely through the admin panel, which eliminates the attack vector but reduces platform functionality. An alternative approach involves implementing a whitelist of approved domains that are permitted for oneboxing, which maintains the feature while limiting potential attack surface. This workaround strategy aligns with security best practices for implementing defense-in-depth measures, where multiple layers of protection are employed to minimize risk exposure. The vulnerability demonstrates the importance of proper input sanitization and resource management in web applications, particularly those that process user-generated content through background processing mechanisms. Organizations should also consider implementing monitoring for unusual memory consumption patterns and automated alerting to detect potential exploitation attempts before they cause significant disruption to platform operations.