Vulnerability Details CVE-2026-15144
@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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.003
EPSS Ranking 16.6%
CVSS Severity
CVSS v3 Score 7.3
References
Products affected by CVE-2026-15144
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cpe:2.3:a:fastify:fastify/rate-limit:0.1.0
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cpe:2.3:a:fastify:fastify/rate-limit:0.1.1
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cpe:2.3:a:fastify:fastify/rate-limit:0.2.0
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cpe:2.3:a:fastify:fastify/rate-limit:0.3.0
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cpe:2.3:a:fastify:fastify/rate-limit:1.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:10.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:10.0.1
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cpe:2.3:a:fastify:fastify/rate-limit:10.1.0
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cpe:2.3:a:fastify:fastify/rate-limit:10.1.1
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cpe:2.3:a:fastify:fastify/rate-limit:10.2.0
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cpe:2.3:a:fastify:fastify/rate-limit:10.2.1
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cpe:2.3:a:fastify:fastify/rate-limit:10.2.2
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cpe:2.3:a:fastify:fastify/rate-limit:10.3.0
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cpe:2.3:a:fastify:fastify/rate-limit:11.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:11.1.0
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cpe:2.3:a:fastify:fastify/rate-limit:2.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:2.0.1
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cpe:2.3:a:fastify:fastify/rate-limit:2.1.0
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cpe:2.3:a:fastify:fastify/rate-limit:2.1.1
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cpe:2.3:a:fastify:fastify/rate-limit:2.2.0
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cpe:2.3:a:fastify:fastify/rate-limit:2.3.0
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cpe:2.3:a:fastify:fastify/rate-limit:2.4.0
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cpe:2.3:a:fastify:fastify/rate-limit:3.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:3.0.1
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cpe:2.3:a:fastify:fastify/rate-limit:4.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:4.0.1
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cpe:2.3:a:fastify:fastify/rate-limit:4.0.2
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cpe:2.3:a:fastify:fastify/rate-limit:4.0.3
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cpe:2.3:a:fastify:fastify/rate-limit:4.1.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.0.1
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cpe:2.3:a:fastify:fastify/rate-limit:5.1.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.2.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.3.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.4.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.4.1
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cpe:2.3:a:fastify:fastify/rate-limit:5.5.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.6.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.6.1
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cpe:2.3:a:fastify:fastify/rate-limit:5.6.2
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cpe:2.3:a:fastify:fastify/rate-limit:5.7.0
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cpe:2.3:a:fastify:fastify/rate-limit:5.7.1
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cpe:2.3:a:fastify:fastify/rate-limit:5.7.2
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cpe:2.3:a:fastify:fastify/rate-limit:5.8.0
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cpe:2.3:a:fastify:fastify/rate-limit:6.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:6.0.1
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cpe:2.3:a:fastify:fastify/rate-limit:7.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:7.1.0
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cpe:2.3:a:fastify:fastify/rate-limit:7.2.0
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cpe:2.3:a:fastify:fastify/rate-limit:7.3.0
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cpe:2.3:a:fastify:fastify/rate-limit:7.4.0
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cpe:2.3:a:fastify:fastify/rate-limit:7.5.0
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cpe:2.3:a:fastify:fastify/rate-limit:7.6.0
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cpe:2.3:a:fastify:fastify/rate-limit:8.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:8.0.1
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cpe:2.3:a:fastify:fastify/rate-limit:8.0.2
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cpe:2.3:a:fastify:fastify/rate-limit:8.0.3
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cpe:2.3:a:fastify:fastify/rate-limit:8.1.0
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cpe:2.3:a:fastify:fastify/rate-limit:8.1.1
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cpe:2.3:a:fastify:fastify/rate-limit:9.0.0
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cpe:2.3:a:fastify:fastify/rate-limit:9.0.1
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cpe:2.3:a:fastify:fastify/rate-limit:9.1.0