vulnerability / NVI-00014070 / Revision 2
Better Auth affected by external request basePath modification DoS
GitHub lists this reviewed advisory for better-auth. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
0.455%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.39508. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
better-auth
source listed< 1.4.2
# 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: Here's the call to `getBaseURL()`, the result is assigned to `ctx.baseURL`. Here's the router receiving the poisoned `basePath`: <img width="594"
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-569q-mpph-wgww ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2025-71401 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.