Better Auth's rou3 Dependency has Double-Slash Path Normalization which can Bypass disabledPaths Config and Rate Limits

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.6 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

EPSS

• CVE-2025-71399: 0.52% estimated exploitation activity in the next 30 days; percentile 44.21 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary An issue in the underlying router library rou3 can cause /path and //path to be treated as identical routes. If your environment does not normalize incoming URLs (e.g., by collapsing multiple slashes), this can allow bypasses of disabledPaths and path-based rate limits. Details Better Auth uses better-call, which internally relies on rou3 for routing. Affected versions of rou3 normalize paths by removing empty segments. As a result: /sign-in/email //sign-in/email ///sign-in/email …all resolve to the same route. Some production setups automatically collapse multiple slashes. This includes: Vercel with Nextjs (default) Cloudflare - when normalize to urls origin is enabled (https://developers.cloudflare.com/rules/normalization/settings/#normalize-urls-to-origin) In these environments and other configurations where //path reach Better Auth as /path, the issue does not apply. Fix Updating rou3 to the latest version resolves the issue: better-call previously depended on "rou3":…

Published by the source

16 Dec 2025, 21:22 UTC

Last modified by the source

3 Aug 2026, 03:41 UTC

Source last checked

26 Oct 2026, 12:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-x732-6j76-qmhm

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-x732-6j76-qmhm

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# Patch Next advisory brief: CVE-2025-71399

Advisory: Better Auth's rou3 Dependency has Double-Slash Path Normalization which can Bypass disabledPaths Config and Rate Limits
IDs: CVE-2025-71399, GHSA-x732-6j76-qmhm
Record: https://patchnext.com/advisories/cve-2025-71399 (revision 2, source checked 26 Oct 2026, 12:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: better-auth 1.4.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm better-auth: affected < 1.4.5; fixed in 1.4.5

## Suggested inspection (read-only)
- `npm ls better-auth --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on better-auth.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-x732-6j76-qmhm (OSV record GHSA-x732-6j76-qmhm lists affected ranges: npm better-auth >=0 <1.4.5 (fixed))
- Verified: https://github.com/advisories/GHSA-x732-6j76-qmhm (GitHub-reviewed advisory GHSA-x732-6j76-qmhm lists affected ranges: npm better-auth >=0 <1.4.5)

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