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.
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History
Fri, 29 May 2026 19:30:00 +0000
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Fri, 29 May 2026 01:15:00 +0000
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Thu, 28 May 2026 22:15:00 +0000
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| 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. | |
| Title | Better Auth: Rate limiter keys IPv6 addresses individually and is bypassable via prefix rotation | |
| Weaknesses | CWE-307 | |
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-05-29T19:05:38.845Z
Reserved: 2026-05-12T00:51:29.085Z
Link: CVE-2026-45364
Updated: 2026-05-29T19:05:31.273Z
Status : Received
Published: 2026-05-28T22:17:00.633
Modified: 2026-05-28T22:17:00.633
Link: CVE-2026-45364
No data.
OpenCVE Enrichment
Updated: 2026-05-29T01:00:12Z