CVE-2026-53515: better auth Privilege Escalation — Fix

Description

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.

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CVSS v3.1 Score

7.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N

EPSS — Exploit Prediction

0.0024

Probability of exploitation

0.15%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-269 CWE-269

CWE-285 CWE-285

CWE-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
better-auth	better-auth\/sso	< 1.6.11
better-auth	better_auth	1.2.10 — 1.6.11

References

Advisories & Patches

https://github.com/better-auth/better-auth/commit/86765f1597378f5c3deed1b80ca91faac0a6bf00 https://github.com/better-auth/better-auth/pull/9220 https://github.com/better-auth/better-auth/security/advisories/GHSA-gv74-j8m3-fg5f

Other References

https://github.com/better-auth/better-auth/releases/tag/v1.6.11

Frequently Asked Questions

What is CVE-2026-53515? +

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. It has a CVSS v3.1 base score of 7.1 (HIGH).

How severe is CVE-2026-53515? +

CVE-2026-53515 has a CVSS v3.1 score of 7.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0024, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-53515? +

CVE-2026-53515 affects products from better-auth, specifically: better-auth\/sso, better_auth. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-53515? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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