Better Auth URL parameter HTML Injection (Reflected Cross-Site scripting)

Exploitation

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

CVSS 4.0

5.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2025-71404: 0.72% estimated exploitation activity in the next 30 days; percentile 53.93 (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 The better-auth /api/auth/error page was vulnerable to HTML injection, resulting in a reflected cross-site scripting (XSS) vulnerability. Details The value of error URL parameter was reflected as HTML on the error page: https://github.com/better-auth/better-auth/blob/05ada0b79dbcac93cc04ceb79b23ca598d07830c/packages/better-auth/src/api/routes/error.ts#L81 Impact An attacker who exploited this vulnerability by coercing a user to visit a specially-crafted URL could execute arbitrary JavaScript in the context of the user's browser.

Published by the source

5 Feb 2025, 21:49 UTC

Last modified by the source

2 Aug 2026, 03:56 UTC

Source last checked

26 Oct 2026, 12:41 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9x4v-xfq5-m8x5

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9x4v-xfq5-m8x5

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# Patch Next advisory brief: CVE-2025-71404

Advisory: Better Auth URL parameter HTML Injection (Reflected Cross-Site scripting)
IDs: CVE-2025-71404, GHSA-9x4v-xfq5-m8x5
Record: https://patchnext.com/advisories/cve-2025-71404 (revision 3, 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: Medium (CVSS 5.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: better-auth 1.1.16. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm better-auth: affected >= 0.0.2, < 1.1.16; fixed in 1.1.16

## 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-9x4v-xfq5-m8x5 (OSV record GHSA-9x4v-xfq5-m8x5 lists affected ranges: npm better-auth >=0.0.2 <1.1.16 (fixed))
- Verified: https://github.com/advisories/GHSA-9x4v-xfq5-m8x5 (GitHub-reviewed advisory GHSA-9x4v-xfq5-m8x5 lists affected ranges: npm better-auth >=0.0.2 <1.1.16)

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