better-auth: OAuth Proxy lets an attacker sign in as another user

{
  "id": "487dcad0848ae4fb0ae3d56caf8361acc615e3e5c51ee697ed4a93a4fe77b2f1",
  "url": "https://osv.dev/vulnerability/GHSA-r4xp-prcw-77qf",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "better-auth: OAuth Proxy lets an attacker sign in as another user",
    "summary": "## Am I affected? You may be affected if you use `better-auth` from 1.5.0-beta.12 through versions before 1.7.7 with the OAuth Proxy plugin. You are affected only if **all** of these are also true: - On a participating environment, the OAuth Proxy plugin has no dedicated `secret`, or its `secret` equals that environment's global Better Auth secret. - Sign-in state is stored in a cookie (`account.storeStateStrategy: \"cookie\"`). With a database or secondary storage, this is only the case if you chose it explicitly. - Implicit account linking is on (the default). You are not affected by this path if every participating environment uses a proxy `secret` distinct from its global Better Auth secret, if sign-in state is stored in the database, or if you use a version before 1.5.0-beta.12. ## Summary The OAuth Proxy plugin trusts any user profile it can decrypt. In the affected setup, Better Auth encrypts sign-in state, including data the caller chose, with the same secret and hands it to anyone who starts a social sign-in. An attacker can use this to get a fake profile for another user's email address that the proxy accepts as real. ## Impact An attacker without an account who knows a user's verified email address can sign in as that user, with that user's permissions. They can read private data, change the account, and link a provider account of their choice to it. They need no provider sign-in and no action from the victim. No availability impact is established, and a reported ope",
    "evidence": "osv:GHSA-r4xp-prcw-77qf",
    "products": [
      {
        "name": {
          "value": "better-auth",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.7.7",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "GHSA-r4xp-prcw-77qf",
      "aliases": [
        "CVE-2026-110864",
        "GHSA-r4xp-prcw-77qf"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "1.5.0-beta.12"
                },
                {
                  "fixed": "1.7.7"
                }
              ]
            }
          ],
          "package": {
            "name": "better-auth",
            "purl": "pkg:npm/better-auth",
            "ecosystem": "npm"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-r4xp-prcw-77qf/GHSA-r4xp-prcw-77qf.json"
          }
        }
      ],
      "modified": "2026-10-27T15:47:24.832632558Z",
      "provider": "osv",
      "references": [
        "https://github.com/better-auth/better-auth/security/advisories/GHSA-r4xp-prcw-77qf",
        "https://github.com/better-auth/better-auth/pull/11494",
        "https://github.com/better-auth/better-auth/commit/ac54bfd67821a7607533af2059858b12bc54e26a",
        "https://github.com/better-auth/better-auth",
        "https://github.com/better-auth/better-auth/releases/tag/v1.7.7"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-287",
          "CWE-345"
        ],
        "severity": "HIGH",
        "github_reviewed": true,
        "nvd_published_at": null,
        "github_reviewed_at": "2026-10-27T15:32:16Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-110864",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 462841,
  "published_at": "2026-10-27T15:32:16+00:00"
}