Better Auth relies on better-call, which uses the rou3 router library. (CVE-2025-71399)
Better Auth versions prior to 1.4.5 rely on the rou3 router library, which normalizes URL paths by removing empty segments. This behavior causes different URL paths with extra slashes (e.g., /path, //path, ///path) to resolve to the same route. As a result, attackers can bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL. This vulnerability does not affect deployments where the proxy or platform normalizes URLs by collapsing multiple slashes. The issue is fixed in Better Auth version 1.4.5, which bundles the fixed rou3 library.
AI Analysis
Technical Summary
The vulnerability (CVE-2025-71399) arises from Better Auth's dependency on the rou3 router library, which normalizes URL paths by removing empty segments. In affected rou3 versions, paths like /path, //path, and ///path are treated equivalently. In Better Auth versions before 1.4.5, this allows attackers to circumvent disabledPaths configuration and path-based rate limits by crafting URLs with extra slashes. Deployments that normalize URLs at the proxy or platform level are not affected. The fix is included in Better Auth 1.4.5, which bundles an updated rou3 library that addresses this issue.
Potential Impact
Attackers can bypass security controls such as disabledPaths and path-based rate limits by exploiting the URL path normalization behavior, potentially leading to unauthorized access or denial of service conditions. The vulnerability affects confidentiality, integrity, and availability as indicated by the CVSS vector (C:L, I:L, A:H).
Mitigation Recommendations
Upgrade Better Auth to version 1.4.5 or later, which includes the fixed rou3 router library. If upgrading is not immediately possible, ensure that the deployment environment (proxy or platform) normalizes URLs by collapsing multiple slashes to mitigate the issue. Patch status is not explicitly stated beyond the fixed version 1.4.5; check vendor advisories for the latest remediation guidance.
Better Auth relies on better-call, which uses the rou3 router library. (CVE-2025-71399)
Description
Better Auth versions prior to 1.4.5 rely on the rou3 router library, which normalizes URL paths by removing empty segments. This behavior causes different URL paths with extra slashes (e.g., /path, //path, ///path) to resolve to the same route. As a result, attackers can bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL. This vulnerability does not affect deployments where the proxy or platform normalizes URLs by collapsing multiple slashes. The issue is fixed in Better Auth version 1.4.5, which bundles the fixed rou3 library.
CVSS v3.1
Score 8.6high
Affected software
pkg:github/better-auth/better-authRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability (CVE-2025-71399) arises from Better Auth's dependency on the rou3 router library, which normalizes URL paths by removing empty segments. In affected rou3 versions, paths like /path, //path, and ///path are treated equivalently. In Better Auth versions before 1.4.5, this allows attackers to circumvent disabledPaths configuration and path-based rate limits by crafting URLs with extra slashes. Deployments that normalize URLs at the proxy or platform level are not affected. The fix is included in Better Auth 1.4.5, which bundles an updated rou3 library that addresses this issue.
Potential Impact
Attackers can bypass security controls such as disabledPaths and path-based rate limits by exploiting the URL path normalization behavior, potentially leading to unauthorized access or denial of service conditions. The vulnerability affects confidentiality, integrity, and availability as indicated by the CVSS vector (C:L, I:L, A:H).
Mitigation Recommendations
Upgrade Better Auth to version 1.4.5 or later, which includes the fixed rou3 router library. If upgrading is not immediately possible, ensure that the deployment environment (proxy or platform) normalizes URLs by collapsing multiple slashes to mitigate the issue. Patch status is not explicitly stated beyond the fixed version 1.4.5; check vendor advisories for the latest remediation guidance.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-9fq7-6g6p-g9rm
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2025-71399"]
- Ecosystems
- []
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a6fb62bbf32cb7a346e714f
Added to database: 08/02/2026, 21:27:07 UTC
Last enriched: 08/02/2026, 21:29:05 UTC
Last updated: 08/03/2026, 00:03:08 UTC
Views: 4
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