CVE-2025-57816 is a medium-severity vulnerability affecting ethyca's open-source privacy engineering platform, Fides, specifically versions prior to 2.69.1. The vulnerability stems from improper control of interaction frequency (CWE-799) in the Fides Webserver API's built-in IP-based rate limiting mechanism. In environments utilizing content delivery networks (CDNs), proxies, or load balancers, the rate limiting is ineffective because it incorrectly applies limits based on the IP addresses of directly connected infrastructure components rather than the true client IP addresses. Additionally, the rate limiting counters are stored in-memory on individual servers instead of a centralized or shared store, which prevents consistent enforcement across distributed instances. This design flaw allows attackers to bypass intended rate limits by distributing requests across multiple infrastructure IPs or servers, enabling them to send a high volume of requests without triggering throttling. The primary risk is a denial of service (DoS) condition, where attackers can overwhelm the Fides Webserver API, potentially degrading service availability or causing outages. The vulnerability only impacts deployments relying solely on Fides's built-in rate limiting; those using external rate limiting solutions such as Web Application Firewalls (WAFs) or API gateways are not affected. The issue was addressed in version 2.69.1 of Fides by correcting the IP identification logic and presumably improving rate limit state sharing. There are no application-level workarounds, but external infrastructure-level rate limiting can mitigate the risk. No known exploits are reported in the wild as of the publication date. The CVSS 4.0 base score is 6.3, reflecting a network attack vector with low complexity, no privileges or user interaction required, and limited impact on availability only.

For European organizations using Fides versions prior to 2.69.1 with the built-in rate limiting enabled and without external rate limiting controls, this vulnerability poses a risk of denial of service. Such DoS attacks could disrupt privacy engineering workflows, data processing, or compliance-related operations that rely on Fides, potentially impacting GDPR compliance efforts or other data protection activities. The inability to effectively rate limit client requests could also lead to resource exhaustion on servers, causing service degradation or outages. While the vulnerability does not directly compromise confidentiality or integrity, availability impacts can have downstream effects on business continuity and regulatory compliance. Organizations in sectors with stringent privacy requirements, such as finance, healthcare, and government, may face operational and reputational risks if their privacy engineering platforms are disrupted. However, the impact is mitigated if organizations have deployed external rate limiting solutions at the infrastructure level, which is common in enterprise environments. Since no exploits are known in the wild, the immediate threat level is moderate, but the vulnerability should be addressed proactively to prevent potential abuse.

European organizations should upgrade all Fides deployments to version 2.69.1 or later to remediate the vulnerability directly. For environments where immediate upgrading is not feasible, implementing external rate limiting at the infrastructure level is critical. This can be achieved by configuring Web Application Firewalls (WAFs), API gateways, or load balancers to enforce client IP-based rate limits, ensuring that rate limiting is applied consistently regardless of underlying infrastructure IPs. Organizations should verify that these external controls correctly identify and use the original client IP, typically by inspecting HTTP headers such as X-Forwarded-For or using proxy protocol features. Additionally, monitoring and alerting on unusual traffic patterns or spikes to the Fides API can help detect potential abuse attempts early. Network segmentation and limiting exposure of the Fides API to trusted networks or VPNs can further reduce attack surface. Finally, organizations should review their incident response plans to include scenarios involving DoS attacks against privacy engineering platforms.