GHSA-9x4v-xfq5-m8x5: Better auth Cross-Site Scripting Vulnerability

MODERATE
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CWE-79
Published
Advisory Summary

GHSA-9x4v-xfq5-m8x5 is a MODERATE cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Better auth libraries in the npm ecosystem. The issue involves better auth url parameter html injection (reflected cross-site scripting). Remediation is available by upgrading affected packages to version 1.1.16.

GHSA-9x4v-xfq5-m8x5 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-9x4v-xfq5-m8x5
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Better auth
Package Ecosystem npm
Published Date
Last Updated

How to Fix GHSA-9x4v-xfq5-m8x5

To remediate this vulnerability, upgrade all affected Better auth dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

better-auth fixed: 1.1.16 
npm install better-auth@1.1.16
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls better-auth

How to Check if You Are Affected

To determine whether your Node.js application is affected by GHSA-9x4v-xfq5-m8x5, inspect your project dependencies using npm:

npm ls better-auth

Analyze the terminal output to locate any version of Better auth in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.1.16), your application is affected.

Note: The npm ls better-auth command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Better auth, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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.

GHSA-9x4v-xfq5-m8x5 Affected Better auth Versions

1 component(s)
Fixed Versions:
1.1.16
Product / Package Ecosystem Affected Versions Fixed Version
better-auth
npm/better-auth
npm
≥ 0.0.2
< 1.1.16
1.1.16

References

GitHub Advisory / Wiki ADVISORY
https://github.com/better-auth/better-auth/security/advisories/GHSA-9x4v-xfq5-m8x5
Security Fix Commit FIX COMMIT
https://github.com/better-auth/better-auth/commit/7ae340e2eddad641b7e43d24d37c58a66ce9ddcf
Better auth Source Repository REPOSITORY
https://github.com/better-auth/better-auth
Better auth Source Repository REPOSITORY
https://github.com/better-auth/better-auth/blob/05ada0b79dbcac93cc04ceb79b23ca598d07830c/packages/better-auth/src/api/routes/error.ts#L81

Frequently Asked Questions

What is GHSA-9x4v-xfq5-m8x5?
GHSA-9x4v-xfq5-m8x5 is a security vulnerability in Better auth involving Better Auth URL parameter HTML Injection (Reflected Cross-Site scripting) under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Better auth versions are affected?
Affected versions include releases prior to 1.1.16 across affected packages: better-auth.
What version fixes GHSA-9x4v-xfq5-m8x5?
Upgrading to 1.1.16 (or the latest patched release for your respective branch) resolves the vulnerability.
Is better-auth affected?
Yes, better-auth is affected in releases prior to 1.1.16. Upgrade your dependency to 1.1.16 or later.
What CWE is associated with GHSA-9x4v-xfq5-m8x5?
GHSA-9x4v-xfq5-m8x5 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check npm dependencies for GHSA-9x4v-xfq5-m8x5?
Run the dependency tree command: 'npm ls better-auth'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9x4v-xfq5-m8x5",
  "modified" : "2025-12-09T16:26:23Z",
  "published" : "2025-02-05T21:49:39Z",
  "aliases" : [ ],
  "summary" : "Better Auth URL parameter HTML Injection (Reflected Cross-Site scripting)",
  "details" : "### Summary\nThe better-auth `/api/auth/error` page was vulnerable to HTML injection, resulting in a reflected cross-site scripting (XSS) vulnerability.\n\n### Details\nThe 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\n\n### Impact\nAn 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.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "better-auth"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.0.2"
      }, {
        "fixed" : "1.1.16"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/better-auth/better-auth/security/advisories/GHSA-9x4v-xfq5-m8x5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/better-auth/better-auth/commit/7ae340e2eddad641b7e43d24d37c58a66ce9ddcf"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/better-auth/better-auth"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/better-auth/better-auth/blob/05ada0b79dbcac93cc04ceb79b23ca598d07830c/packages/better-auth/src/api/routes/error.ts#L81"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-02-05T21:49:39Z",
    "nvd_published_at" : null
  }
}