Privilege Escalation in @better-auth/sso (CVE-2026-53515)
Summary
Vulnerability in @better-auth/sso (CVE-2026-53515). Data can be tampered with by attackers. Exploitable via POST /sso/register. Mitigation: upgrade to 1.6.11 or later.
Original description
The description as published by the source.
Better Auth is an authentication and authorization library for TypeScript. From 1.2.10 until 1.6.11, the @better-auth/sso plugin's POST /sso/register endpoint lets any organization member attach a new SSO provider to that organization because registerSSOProvider checks only for a membership row and does not require an owner or admin role, allowing attacker-controlled OIDC or SAML providers to drive /sso/callback/{providerId} organization provisioning. This issue is fixed in version 1.6.11.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-53515 has been found in @better-auth/sso.
Attackers can target a specific entry point like POST /sso/register over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.1/10.
What to do: upgrade @better-auth/sso to 1.6.11 or later.
If unsure, ask your IT team or search "@better-auth/sso CVE-2026-53515" on the vendor's site.
CVE-2026-53515 (@better-auth/sso) — CWE-269 / CVSS v3 7.1
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /sso/register / next / providersLimit / organizationProvisioning.defaultRole
Patched: 1.6.11 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-269) exists in @better-auth/sso. Attackers reach the vulnerable code path via POST /sso/register.
Check the vendor advisory for the affected versions of @better-auth/sso. Attack surface: POST /sso/register / next / providersLimit / organizationProvisioning.defaultRole.
Severity: High (CVSS 7.1/10). Data can be tampered with by attackers.
Update to 1.6.11.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual POST /sso/register requests with malformed payloads or SQL meta-characters. Run grep -r '@better-auth/sso' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r '@better-auth/sso' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
@better-auth/ssoを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'POST /sso/register' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /sso/registerへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade @better-auth/sso to 1.6.11ステージング環境で 1.6.11 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against POST /sso/register on staging to confirm patch closes the vectorパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- patch github.com
- web github.com
- web github.com
- web github.com