CVE-2025-71399

Better Auth before 1.4.5 Path Normalization Bypass via rou3

State
Published
Severity
8.8 High
Published
Aug 2, 2026
Updated
Oct 8, 2026
Reserved
Jul 18, 2026

Read the record on cve.org

Description

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.

Scores

CVSSScoreVectorSource
4.08.8 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:NVulnCheck
3.18.6 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:HVulnCheck

Weaknesses

  • CWE-20 Improper Input Validation

Affected Products

ProductVersions
better-authbetter-auth
  • before 1.4.5Affected
  • 1.4.5Not affected

References

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