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chore(deps): update dependency better-auth to v1.4.5 [security] #6238

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chore(deps): update dependency better-auth to v1.4.5 [security] #6238

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@renovate renovate bot commented Dec 28, 2025

Note: This PR body was truncated due to platform limits.

This PR contains the following updates:

Package Change Age Confidence
better-auth (source) 1.3.27 -> 1.4.5 age confidence

GitHub Vulnerability Alerts

GHSA-569q-mpph-wgww

Summary

Affected versions of Better Auth allow an external request to configure baseURL when it isn’t defined through any other means. This can be abused to poison the router’s base path, causing all routes to return 404 for all users.

This issue is only exploitable when baseURL is not explicitly configured (e.g., BETTER_AUTH_URL is missing) and the attacker is able to make the very first request to the server after startup. In properly configured environments or typical managed hosting platforms, this fallback behavior cannot be reached.

Details

A combination of X-Forwarded-Host and X-Forwarded-Proto is implicitly trusted. This allows the first request to configure baseURL whenever it is not explicitly configured.

Here's the code that reads the headers:

headers

Here's the call to getBaseURL(), the result is assigned to ctx.baseURL.

write

Here's the router receiving the poisoned basePath:

router

X-Forwarded-Host and X-Forwarded-Proto can be used to modify the pathname of a parsed URL object which forms baseURL. basePath is then derived from the pathname of baseURL. Once the router basePath is poisoned it fails to match & route incoming requests.

Repro

Start a better-auth server with no baseURL configuration.

Send the following request as the first request to the server:

curl -i --location 'https://example.com/api/auth/ok' \
--header 'X-Forwarded-Proto: some:' \
--header 'X-Forwarded-Host: junk'

The better-auth API check endpoint returns 404.

Now send a regular request without the X-Forwarded-Proto and X-Forwarded-Host headers.

curl -i --location 'https://example.com/api/auth/ok'

The better-auth API check endpoint still returns 404.

Example result

attack

We have modified the basePath for the router until the server is restarted. An attacker can repeatedly send these attack requests aiming to persistently exploit the vulnerability.

GHSA-x732-6j76-qmhm

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:

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 Auth recommends:

  1. Upgrading to Better Auth v1.4.5 or later, which includes the updated rou3.
  2. Ensuring the proxy normalizes URLs.
  3. 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.

Release Notes

better-auth/better-auth (better-auth)

v1.4.5

Compare Source

v1.4.4

Compare Source

   🚀 Features
   🐞 Bug Fixes
    View changes on GitHub

v1.4.3

Compare Source

   🚀 Features
   🐞 Bug Fixes
    View changes on GitHub

v1.4.2

Compare Source

   🚀 Features
   🐞 Bug Fixes
    View changes on GitHub

v1.4.1

Compare Source

   🚀 Features
   🐞 Bug Fixes
    View changes on GitHub

v1.4.0

Compare Source

   🚀 Features
   🐞 Bug Fixes

Configuration

📅 Schedule: Branch creation - "" (UTC), Automerge - At any time (no schedule defined).

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

  • If you want to rebase/retry this PR, check this box

This PR was generated by Mend Renovate. View the repository job log.

@renovate renovate bot added the dependencies Pull requests that update a dependency file label Dec 28, 2025
@coderabbitai
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coderabbitai bot commented Dec 28, 2025 •
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Important

Review skipped

Review was skipped due to path filters

⛔ Files ignored due to path filters (1)
  • pnpm-lock.yaml is excluded by !**/pnpm-lock.yaml

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nx-cloud bot commented Dec 28, 2025 •
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🤖 Nx Cloud AI Fix Eligible

An automatically generated fix could have helped fix failing tasks for this run, but Self-healing CI is disabled for this workspace. Visit workspace settings to enable it and get automatic fixes in future runs.

To disable these notifications, a workspace admin can disable them in workspace settings.

View your CI Pipeline Execution ↗ for commit 3c4e172

Command Status Duration Result
nx affected --targets=test:eslint,test:unit,tes... ❌ Failed 2m 24s View ↗
nx run-many --target=build --exclude=examples/*... ❌ Failed 53s View ↗

☁️ Nx Cloud last updated this comment at 2025-12-30 01:16:13 UTC

@renovate renovate bot force-pushed the renovate/npm-better-auth-vulnerability branch from e3d03c7 to 3c4e172 Compare December 30, 2025 01:12
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