Is Fly.io Safe?
Last updated: January 12, 2026
An honest security analysis of Fly.io for developers considering it for their projects.
Quick Answer
Safe - use fly secrets and private networkingFly.io is safe for global edge deployments with strong infrastructure (runs Firecracker VMs). 'fly secrets' encrypts credentials. Key difference from Vercel: you manage full Linux containers across 30+ regions. Main concern: multi-region secrets sync must be verified.
Understanding Fly.io Security
When evaluating whether Fly.io is safe for your project, it's important to understand the distinction between platform security and application security. Fly.io as a platform implements industry-standard security practices for its infrastructure, including encryption, access controls, and regular security audits.
However, the security of applications built with Fly.io depends significantly on how developers use the platform. AI-generated code and rapid development workflows can introduce vulnerabilities that exist independently of the platform's underlying security. Research from Stanford University found that AI coding assistants produce vulnerable code approximately 40% of the time when working on security-sensitive tasks.
The most common security issues in Fly.io applications stem from misconfigurations, exposed credentials, and missing security controls—problems that developers must address regardless of which platform they use. Understanding these patterns helps you make informed decisions about using Fly.io for your specific use case.
Platform Security
Platform security refers to the security measures Fly.io implements at the infrastructure level: how they protect their servers, encrypt data in transit and at rest, manage access to their systems, and respond to security incidents. These are controls the platform provider manages on your behalf.
Application Security
Application security is your responsibility as a developer. This includes properly configuring authentication, implementing authorization controls, protecting sensitive data, securing API endpoints, and avoiding common vulnerabilities like exposed credentials or SQL injection. These risks exist regardless of which platform you use.
Common Security Mistakes in Fly.io Apps
Based on security scans of thousands of Fly.io applications, these are the most frequently encountered vulnerabilities. Understanding these patterns helps you proactively secure your applications.
Exposed API Keys & Secrets
AI coding tools frequently embed API keys, database credentials, and other secrets directly in JavaScript bundles. These credentials become visible to anyone who inspects your application's source code in their browser.
Prevention: Use environment variables and server-side API routes to keep credentials secure.
Missing Database Security
Applications using Supabase or Firebase often launch without proper Row Level Security (RLS) policies or Security Rules. This allows unauthorized users to read, modify, or delete data they shouldn't have access to.
Prevention: Always enable and test RLS policies before deploying to production.
Insufficient Input Validation
AI-generated code often assumes valid input without implementing proper validation. This opens applications to injection attacks, XSS vulnerabilities, and data corruption.
Prevention: Validate all user input on both client and server side.
Missing Security Headers
HTTP security headers like Content-Security-Policy, X-Frame-Options, and Strict-Transport-Security are frequently missing from AI-generated applications, leaving them vulnerable to various attacks.
Prevention: Configure security headers in your hosting platform or application middleware.
Security Assessment
Security Strengths
- Firecracker microVMs provide hardware-level isolation (same as AWS Lambda)
- Private Networking: internal WireGuard mesh across all your machines globally
- 'fly secrets' encrypts and syncs credentials across all regions automatically
- Global edge means DDoS traffic is absorbed at 30+ points of presence
- Full container control - run your own security tools inside the VM
Security Concerns
- Multi-region secrets sync can fail silently - verify with 'fly secrets list'
- Persistent Volumes are not encrypted by default - encrypt at app level
- fly.toml config is in repo - don't put secrets in config file
- Network complexity: 6PN, Private Networking, Flycast - easy to misconfigure
- Root access means you own security patching (unlike managed serverless)
Security Checklist for Fly.io
- 1Use 'fly secrets set KEY=value' - never put credentials in fly.toml
- 2Verify secrets in all regions: 'fly secrets list -a your-app'
- 3Enable Private Networking for database ↔ app communication
- 4Encrypt Volumes at application level if storing sensitive data
- 5Use 'fly ips private' to confirm internal communication works
- 6Set up fly-replay headers carefully - secrets may leak in replay
The Verdict
Fly.io is ideal for latency-sensitive global apps. The Firecracker VM isolation is enterprise-grade. Unlike Vercel/Netlify (managed serverless), you control the full stack - which means you also own security patching. Use 'fly secrets' for credentials and Private Networking for internal traffic.
Security Research & Industry Data
Understanding Fly.io security in the context of broader industry trends and research.
of Lovable applications (170 out of 1,645) had exposed user data in the CVE-2025-48757 incident
Source: CVE-2025-48757 security advisory
average cost of a data breach in 2023
Source: IBM Cost of a Data Breach Report 2023
developers using vibe coding platforms like Lovable, Bolt, and Replit
Source: Combined platform statistics 2024-2025
What Security Experts Say
“There's a new kind of coding I call 'vibe coding', where you fully give in to the vibes, embrace exponentials, and forget that the code even exists.”
“Vibe coding your way to a production codebase is clearly risky. Most of the work we do as software engineers involves evolving existing systems, where the quality and understandability of the underlying code is crucial.”
Frequently Asked Questions
How does fly secrets work?
fly secrets encrypts credentials and syncs them across all regions where your app runs. Set with 'fly secrets set KEY=value'. Secrets are injected as environment variables at runtime. Verify deployment with 'fly secrets list' - ensure all regions have the latest values.
Is Fly.io safer than Vercel?
Different models: Fly.io gives you full Linux containers (more control, more responsibility). Vercel abstracts infrastructure (less control, managed security). Fly.io's Firecracker isolation is battle-tested. Choose Fly.io for global edge containers; Vercel for managed serverless.
What is Fly.io Private Networking?
Private Networking creates a WireGuard-encrypted mesh between all your Fly machines globally. Internal traffic uses .internal domains and never touches the public internet. Enable in fly.toml and use internal hostnames for database connections.
Are Fly.io Volumes encrypted?
Fly Volumes are NOT encrypted at rest by default. If storing sensitive data, encrypt at the application level before writing to Volumes. This is different from managed databases like RDS which encrypt by default.
Verify Your Fly.io App Security
Don't guess - scan your app and know for certain. VAS checks for all the common security issues in Fly.io applications.