CVE-2025-57815: Ethyca Fides Auth Bypass Vulnerability

CVE-2025-57815 Overview

CVE-2025-57815 affects Fides, an open-source privacy engineering platform developed by Ethyca. The Admin UI login endpoint relies on a general IP-based rate limit for all API traffic and lacks specific anti-automation controls. This gap exposes the authentication endpoint to credential testing attacks such as credential stuffing and password spraying. Accounts using weak or previously compromised passwords face the highest risk. Version 2.69.1 addresses the issue by introducing dedicated protections at the login endpoint. The weakness is classified under CWE-307: Improper Restriction of Excessive Authentication Attempts.

Critical Impact
Attackers can automate login attempts against the Fides Admin UI without triggering endpoint-specific throttling, enabling credential stuffing and password spraying against exposed instances.

Affected Products

Ethyca Fides versions prior to 2.69.1
Fides Open Source deployments using username/password authentication
Fides Admin UI login endpoint

Discovery Timeline

2025-09-08 - CVE-2025-57815 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-57815

Vulnerability Analysis

The Fides Admin UI authenticates users through a login endpoint that inherits the platform's global API rate limit. The global limit applies uniformly to all API traffic per source IP, so it does not treat login attempts as a sensitive operation requiring stricter thresholds. Attackers distributing requests across proxies, botnets, or cloud IP ranges can stay under the general threshold while still submitting large volumes of credential guesses. The platform lacks account-based lockouts, progressive delays, CAPTCHA challenges, or other anti-automation mechanisms tied to the authentication flow.

Root Cause

The root cause is the absence of authentication-specific rate limiting and anti-automation controls on the Admin UI login route. Reliance on general IP-based limits, mapped to [CWE-307], does not restrict repeated failed authentication attempts against individual accounts. Weak or reused passwords compound the exposure because attackers can validate leaked credentials at scale.

Attack Vector

Exploitation requires only network access to a Fides Admin UI login endpoint. An attacker enumerates valid usernames or reuses credential lists from prior breaches, then submits authentication requests through automated tools. Because throttling is IP-scoped and generous, distributed sources allow high-volume testing. Successful credential validation yields administrative access to the privacy engineering platform.

text

// Security patch: docker/nginx/nginx.conf (Fides 2.69.1)
// Introduces an nginx load balancer in front of Fides webservers,
// enabling upstream logging and centralized request handling for
// authentication traffic.
events {}

http {

  log_format upstream_log '$remote_addr - $remote_user [$time_local] '
                        '"$request" $status $body_bytes_sent '
                        '"$http_referer" "$http_user_agent" '
                        'upstream_addr="$upstream_addr" '
                        'upstream_status="$upstream_status"';

  upstream fides {
    server fides-1:8080;
    server fides-2:8080;
  }

  server {
    listen 8080;
    access_log /dev/stdout upstream_log;

    location / {
      proxy_pass http://fides;
    }
  }
}
// Source: https://github.com/ethyca/fides/commit/59903c195e2f9f8915a1db94950aefd557033a5c

Detection Methods for CVE-2025-57815

Indicators of Compromise

High volume of POST requests to the Fides Admin UI login endpoint from a single IP or narrow IP range
Repeated HTTP 401 or 403 responses from the login endpoint followed by a successful 200 response
Login attempts spanning many usernames from the same source, consistent with password spraying
Authentication requests originating from cloud provider ranges, VPN exit nodes, or residential proxy networks

Detection Strategies

Aggregate authentication logs by source IP, user agent, and target username to surface brute-force patterns
Alert when failed login attempts per account exceed a defined threshold within a rolling window
Correlate successful logins with prior bursts of failed attempts against the same account
Baseline normal Admin UI login volume and flag statistical deviations

Monitoring Recommendations

Ingest Fides Admin UI and reverse proxy access logs into a central SIEM or data lake
Enable nginx upstream_log format introduced in 2.69.1 to capture upstream status per request
Monitor for administrator account logins from unfamiliar geographies or ASNs
Track EPSS drift for CVE-2025-57815 alongside internal exposure signals

How to Mitigate CVE-2025-57815

Immediate Actions Required

Upgrade Fides to version 2.69.1 or later, which adds anti-automation controls to the login endpoint
Rotate credentials for any Admin UI account suspected of exposure to credential stuffing lists
Enforce strong, unique passwords and multi-factor authentication for all administrative users
Restrict Admin UI network exposure to trusted networks or VPN ranges where feasible

Patch Information

Ethyca released the fix in Fides 2.69.1. Review the GitHub Security Advisory GHSA-7q62-r88r-j5gw, the patch commit 59903c1, and the 2.69.1 release notes before upgrading.

Workarounds

Commercial Fides Enterprise licensees can configure Single Sign-On (SSO) through an OIDC provider such as Azure, Google, or Okta and disable username/password authentication entirely
Place the Admin UI behind a reverse proxy or Web Application Firewall (WAF) that enforces strict per-endpoint rate limits and CAPTCHA challenges
Restrict access to the login endpoint using IP allowlists at the network or proxy layer
Monitor authentication logs and alert on brute-force patterns until the upgrade is completed

bash

# Example nginx rate limit for the Fides Admin UI login endpoint
http {
  limit_req_zone $binary_remote_addr zone=fides_login:10m rate=5r/m;

  server {
    listen 8080;

    location /api/v1/login {
      limit_req zone=fides_login burst=5 nodelay;
      limit_req_status 429;
      proxy_pass http://fides;
    }

    location / {
      proxy_pass http://fides;
    }
  }
}