CVE-2022-46159 is a medium-severity vulnerability affecting Discourse, an open-source discussion platform widely used for community forums and collaboration. The vulnerability arises from improper resource allocation controls (CWE-770) in Discourse versions 2.8.13 and earlier on the stable branch, as well as versions 2.9.0.beta0 through 2.9.0.beta14 on the beta and tests-passed branches. Specifically, any authenticated user can create unlisted topics—topics that are not visible or readily accessible to other users. Because these unlisted topics consume server resources such as database storage, memory, and processing power without effective limits or throttling, an attacker could exploit this to create a large number of such topics, leading to resource exhaustion. This could degrade the performance of the Discourse instance, potentially causing denial of service (DoS) conditions. The vulnerability does not require elevated privileges beyond authentication, nor does it require user interaction beyond the creation of topics. There are no known workarounds, but a patch addressing this issue is available in the main branch of Discourse. No known exploits have been reported in the wild to date.

For European organizations using Discourse as a community or collaboration platform, this vulnerability could lead to service degradation or denial of service due to resource exhaustion. This can affect the availability and reliability of communication channels critical for internal collaboration, customer engagement, or public forums. While the confidentiality and integrity of data are not directly impacted, the disruption of service availability can have significant operational and reputational consequences. Organizations with large user bases or those that allow broad authenticated user access are at higher risk. Additionally, sectors relying on timely and continuous communication—such as government agencies, educational institutions, and critical infrastructure operators—may experience amplified impacts. The lack of known exploits reduces immediate risk, but the ease of exploitation (any authenticated user can trigger the issue) means that insider threats or compromised accounts could be leveraged to cause disruption.

European organizations should promptly upgrade Discourse installations to the latest main branch version where the patch is applied. Since no workarounds exist, patching is the primary mitigation. Additionally, organizations can implement the following practical controls: 1) Restrict topic creation permissions to trusted user groups to limit potential abuse. 2) Monitor the number of unlisted topics created per user and implement custom rate limiting or alerting mechanisms to detect anomalous activity. 3) Employ resource monitoring on servers hosting Discourse to identify unusual spikes in resource consumption early. 4) Consider deploying web application firewalls (WAFs) with custom rules to detect and throttle excessive topic creation requests. 5) Regularly audit user accounts and enforce strong authentication to reduce the risk of compromised credentials being used to exploit this vulnerability. 6) Engage with the Discourse community or vendor for updates and best practices related to this vulnerability.