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Vulnerability record · CVE-2025-71399 · published 2 August 2026

CVE-2025-71399: Improper input validation vulnerability

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.

8.8 CVSS 4.0 High EPSS 0.52% · top 58.2% CWE-20 · Improper input validation Awaiting Analysis
8.8CVSS 4.0 base score
0.52%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
16 Sep 2026Last modified by NVD

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.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/better-auth/better-auth/commit/f60b43fa648399534507c9ac7db36d705b8874c3
https://github.com/better-auth/better-auth/security/advisories/GHSA-x732-6j76-qmhm
https://www.vulncheck.com/advisories/better-auth-before-path-normalization-bypass-via-rou3

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Source: NIST National Vulnerability Database (record CVE-2025-71399), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.