@fastify/rate-limit vulnerable to rate-limit bypass via IPv6 address rotation

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-15144
StatePUBLISHED
Assigneropenjs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-29 17:16:50 UTC
Updated2026-08-05 15:33:13 UTC
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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS: 0.002460000 probability, percentile 0.159150000 (date 2026-08-09)

Problem Types: CWE-307 | CWE-770 | CWE-307 CWE-307: Improper Restriction of Excessive Authentication Attempts | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
3.1ce714d77-add3-4f53-aff5-83d477b104bbSecondary7.3HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
3.1CNACVSS7.3HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Fastify Fastify/rate-limit All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA @fastifyrate-limit @fastify/rate-limit affected 11.2.0 semver Not specified
CNA @fastifyrate-limit @fastify/rate-limit unaffected 11.2.0 semver Not specified

References

ReferenceSourceLinkTags
cna.openjsf.org/security-advisories.html ce714d77-add3-4f53-aff5-83d477b104bb cna.openjsf.org Vendor Advisory
github.com/fastify/fastify-rate-limit/security/advisories/GHSA-grpc-p53c... ce714d77-add3-4f53-aff5-83d477b104bb github.com Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: 0xShemesh (en)

CNA: mcollina (en)

CNA: climba03003 (en)

CNA: UlisesGascon (en)

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