# CVE-2025-71399 — better-auth

> As of 2026-08-03, CVE-2025-71399 is a HIGH-severity vulnerability in better-auth, CVSS v3.1 8.6, EPSS 0.3% (22.9th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2025-71399 as of 2026-08-03; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-08-03

## What is CVE-2025-71399?

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.

The record classifies CVE-2025-71399 under weakness class [CWE-20](https://intel.threadlinqs.com/cwe/CWE-20). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 64 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 8.6 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H`)
- **CVSS v4.0 base score:** 8.8 (`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`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 22.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-02, last modified 2026-08-03

## Is CVE-2025-71399 being exploited?

It currently carries a trending score of 35 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **better-auth**: better-auth

## How to fix CVE-2025-71399

No vendor patch reference has been recorded for CVE-2025-71399 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2025-71399

No threat campaign in the Threadlinqs corpus currently references CVE-2025-71399, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-08-04. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com — vendor advisory](https://github.com/better-auth/better-auth/security/advisories/GHSA-x732-6j76-qmhm)
- [github.com — patch](https://github.com/better-auth/better-auth/commit/f60b43fa648399534507c9ac7db36d705b8874c3)

**Third-party advisory**

- [vulncheck.com — third party advisory](https://www.vulncheck.com/advisories/better-auth-before-path-normalization-bypass-via-rou3)

Canonical: https://intel.threadlinqs.com/cve/CVE-2025-71399
Full detection coverage and IOCs for threats exploiting CVE-2025-71399 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp