Vulnerability 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 Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/better-auth/better-auth/commit/43e719bcc0c223c7079fa0c611a9cf
- https://github.com/better-auth/better-auth/commit/57af0f7b910dcf7b1a5c0615d10b9b
- 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-h6
FAQ
What is CVE-2026-45364?
CVE-2026-45364 is a vulnerability with a CVSS score of 7.3 (HIGH). 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 recei...
How severe is CVE-2026-45364?
CVE-2026-45364 has been rated HIGH with a CVSS base score of 7.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-45364?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.