{"cve":"CVE-2026-45364","nvd":{"published":"2026-05-28T22:17:00.633","modified":"2026-07-21T10:10:00.103","status":"Deferred","description":"Better Auth is an authentication and authorization library for TypeScript. Prior to 1.4.17 and 1.5.0-beta.9, Better Auth's HTTP rate limiter keyed each request by the exact textual IP address it received in x-forwarded-for (or the configured IP-bearing header). IPv6 clients controlling a typical /64 allocation could rotate through 2^64 distinct source addresses without exhausting the per-address counter, defeating rate limiting on /sign-in/email, /sign-up/email, /forget-password, and every other path the limiter protects. The same bug allowed a single client to vary the textual encoding of one IPv6 address (uppercase, compression, IPv4-mapped, hex-encoded IPv4-in-IPv6) and produce multiple distinct keys. This vulnerability is fixed in 1.4.17 and 1.5.0-beta.9.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L","score":7.3},"cwes":["CWE-307"],"references":["https://github.com/better-auth/better-auth/commit/43e719bcc0c223c7079fa0c611a9cf7ea1188254","https://github.com/better-auth/better-auth/commit/57af0f7b910dcf7b1a5c0615d10b9bd56bb69bef","https://github.com/better-auth/better-auth/pull/7470","https://github.com/better-auth/better-auth/pull/7509","https://github.com/better-auth/better-auth/security/advisories/GHSA-p6v2-xcpg-h6xw"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:36:28.938604137+00:00"},"epss":{"cve":"CVE-2026-45364","score":0.00295,"percentile":0.22146,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-p6v2-xcpg-h6xw","url":"https://osv.dev/vulnerability/GHSA-p6v2-xcpg-h6xw","summary":"Better Auth: Rate limiter keys IPv6 addresses individually and is bypassable via prefix rotation","modified":"2026-06-09T10:30:12.794111806Z","packages":[{"ecosystem":"npm","name":"better-auth","purl":"pkg:npm/better-auth","ranges":["<1.4.17"],"fixed":["1.4.17"]},{"ecosystem":"npm","name":"better-auth","purl":"pkg:npm/better-auth","ranges":[">=1.5.0-beta.1 <1.5.0-beta.9"],"fixed":["1.5.0-beta.9"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}