CVE-2022-31110 is a medium-severity vulnerability classified under CWE-400 (Uncontrolled Resource Consumption) affecting the open-source RSS feed generator RSSHub, developed by DIYgod. The vulnerability exists in versions prior to commit 5c4177441417b44a6e45c3c63e9eac2504abeb5b. Specifically, when specially crafted values are passed to the 'filter' and 'filterout' parameters, the application experiences abnormally high CPU usage. This excessive consumption of processing resources can degrade server performance significantly, potentially leading to denial of service (DoS) conditions where legitimate users are unable to access RSSHub services. The root cause is the lack of proper input validation or resource usage controls on these parameters, allowing attackers to trigger computationally expensive operations. No known workarounds exist, but the issue has been addressed and fixed in the referenced commit, and users are strongly advised to upgrade to the patched version. There are no known exploits in the wild at this time, but the vulnerability poses a risk to service availability, especially for deployments exposed to untrusted users or the public internet.

For European organizations utilizing RSSHub, particularly those relying on it for aggregating and distributing RSS feeds for news, monitoring, or internal communications, this vulnerability could lead to service disruptions. An attacker exploiting this flaw could cause high CPU utilization on servers running vulnerable RSSHub versions, resulting in degraded performance or complete denial of service. This could interrupt critical information flows, delay updates, or impact dependent business processes. Organizations with public-facing RSSHub instances are at higher risk, as attackers can remotely trigger the resource exhaustion without authentication or user interaction. The impact is primarily on availability, but indirect effects on organizational productivity and reputation may occur if services are disrupted. Given RSSHub's open-source nature and adoption in various sectors, including media, IT, and government, the vulnerability could affect a broad range of European entities. However, the absence of known exploits reduces immediate risk, though proactive patching is essential to prevent future attacks.

1. Immediate upgrade to the fixed version of RSSHub, incorporating commit 5c4177441417b44a6e45c3c63e9eac2504abeb5b or later, is the primary and most effective mitigation. 2. Implement input validation and rate limiting on the 'filter' and 'filterout' parameters at the application or web server level to restrict the complexity and frequency of requests, reducing the risk of resource exhaustion. 3. Deploy Web Application Firewalls (WAFs) with custom rules to detect and block suspicious parameter values that could trigger excessive CPU usage. 4. Monitor server CPU and resource utilization closely for unusual spikes that may indicate exploitation attempts. 5. Isolate RSSHub instances behind authentication or VPNs where possible, limiting exposure to untrusted users. 6. Consider containerization or resource capping (e.g., using cgroups or Kubernetes resource limits) to prevent a single process from consuming excessive server resources. 7. Maintain regular backups and have incident response plans ready to restore services quickly in case of DoS events.