CyberRota Analysis
AI-GeneratedThe @fastify/rate-limit package prior to version 11.2.0 is vulnerable as it allows IPv6 clients to bypass rate limits by exploiting the variability in IPv6 address representations and address ranges. This can lead to unauthorized access to protected endpoints, such as authentication and API calls, particularly for applications that trust the client IP when behind a proxy. Developers and organizations using this package should prioritize upgrading to version 11.2.0 or later to mitigate this high-severity vulnerability.
Public Exploit Signal
A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.
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Original NVD Description
@fastify/rate-limit before 11.2.0 keys rate-limit buckets by the verbatim client IP string returned from request.ip. Because a single IPv6 client can control a large address range (a /64 holds 2^64 distinct addresses) and the same address has multiple valid textual representations, an IPv6 capable client can defeat the rate-limit boundary by rotating addresses or by rewriting the same address in different forms. Applications that use @fastify/rate-limit to protect endpoints such as authentication, password reset, OTP delivery, or expensive API calls can be bypassed by IPv6 clients behind a proxy that surfaces IPv6 to the origin when trustProxy is enabled. The issue is fixed in @fastify/rate-limit 11.2.0, where the default key generator normalizes IPv6 addresses to their canonical form, collapses IPv4 mapped IPv6 to IPv4, and applies a configurable prefix mask (default /64) via a new ipv6Subnet option.
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