CVE-2026-15144
HIGHDescription
@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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Exploit Intelligence
Low risk: more likely to be exploited than 16% of all known CVEs.
References
Related Vulnerabilities
Other CWE-307 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2019-17240 | Critical | 9.8 | 40% | - | - |
| CVE-2023-29301 | High | 7.5 | 32% | - | - |
| CVE-2023-22960 | High | 7.5 | 28% | - | Fix |
| CVE-2020-15906 | Critical | 9.8 | 27% | - | Fix |
| CVE-2016-9361 | Critical | 9.8 | 20% | - | - |
| CVE-2024-39225 | Critical | 9.8 | 14% | - | - |
Common questions
How do I fix CVE-2026-15144?
Upgrade fastify\/rate-limit to 11.2.0 or later.
Is CVE-2026-15144 being actively exploited?
Not that we know of. CVE-2026-15144 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.25% is the estimated probability that it will be exploited in the next 30 days. That is higher than 16% of all scored CVEs.
How severe is CVE-2026-15144?
CVE-2026-15144 has a CVSS v3 base score of 7.3, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-15144 affect?
Published advisories record a fix for fastify\/rate-limit (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-05.