GHSA-x732-6j76-qmhm — better-auth
HIGHGHSA-x732-6j76-qmhm is a high-severity (CVSS 8.6) Improper Input Validation vulnerability in better-auth. A fix is available for better-auth — see the affected versions and patch details below.
Better Auth's rou3 Dependency has Double-Slash Path Normalization which can Bypass disabledPaths Config and Rate Limits
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-x732-6j76-qmhm.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-x732-6j76-qmhm plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
better-authnpmDescription
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": "^0.5.1" - The fix was introduced after that version (commit: https://github.com/h3js/rou3/commit/f60b43fa648399534507c9ac7db36d705b8874c3)
Better Auth recommends:
- Upgrading to Better Auth v1.4.5 or later, which includes the updated rou3.
- Ensuring the proxy normalizes URLs.
- If project maintainers cannot upgrade yet, they can protect their app by normalizing url before it reaches better-auth handler. See example below:
const req = new Request(...) // this would be the actual request object
const url = new URL(req.url);
const normalizedPath = url.pathname.replace(/\/+/g, "/");
if (url.pathname !== normalizedPath) {
url.pathname = normalizedPath;
// Update the raw request pathname
Object.defineProperty(req, "url", {
value: url.toString(),
writable: true,
configurable: true,
});
}
Impact
- Bypass
disabledPaths - Bypass path-based rate limits
The impact of bypassing disabled paths could vary based on a project's configuration.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | better-auth | all versions | 1.4.5npm install better-auth@1.4.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for better-auth, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update better-auth to 1.4.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x732-6j76-qmhm is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-x732-6j76-qmhm can be triaged on real exposure rather than presence alone.
Tailored to GHSA-x732-6j76-qmhm. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-x732-6j76-qmhm in your dependencies?
O3 Security finds GHSA-x732-6j76-qmhm across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.