CVSS 3.1
7.3 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:LCVE-2026-45364
High (7.3). EPSS 0.3% chance of exploitation in the next 30 days. Fixed in better-auth 1.4.17, 1.5.0-beta.9.
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.
Severity
- EPSS
- 0.3% chance of exploitation in the next 30 days; higher than 22% of CVEs (scores of 2026-10-31)
- CWE
- CWE-307
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-p6v2-xcpg-h6xw | npm | better-auth | <1.4.17 | 1.4.17 |
| GHSA-p6v2-xcpg-h6xw | npm | better-auth | >=1.5.0-beta.1 <1.5.0-beta.9 | 1.5.0-beta.9 |
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