CVE-2025-71399 PUBLISHED

Better Auth before 1.4.4 Path Normalization Bypass via rou3

Assigner: VulnCheck
Reserved: 18.07.2026 Published: 02.08.2026 Updated: 02.08.2026

Better Auth relies on better-call, which uses the rou3 router library. In affected versions of rou3, paths are normalized by removing empty segments, so /path, //path, and ///path resolve to the same route. In Better Auth versions prior to 1.4.5 (which bundles the fixed rou3), this can allow attackers to bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL path. The issue does not apply in deployments where the proxy or platform normalizes URLs by collapsing multiple slashes.

Metrics

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N
CVSS Score: 8.8

Product Status

Vendor better-auth
Product better-auth
Versions Default: unaffected
  • affected from 0 to 1.4.4 (excl.)
  • Version 1.4.4 is unaffected

Credits

  • goksan reporter

References

Problem Types

  • Improper Input Validation CWE