better-auth versions before 1.6.11 contain insecure cryptographic defaults in the oidcProvider and mcp plugins that advertise the none algorithm and accept plain PKCE by default. Attackers can exploit algorithm negotiation to accept unsigned tokens or intercept authorization codes when PKCE plain is used instead of the required S256 method.

Attack Vector Network

Attack Complexity High

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact High

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact High

Subsequent System Integrity Impact High

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Changed

Confidentiality Impact High

Integrity Impact High

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
better-auth better-auth unaffected
Version Status Constraints
0 affected < 1.6.11
1.6.11 unaffected —

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Project Subscriptions

Vendors Products
Better-auth Subscribe
Better-auth\/oauth-provider Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/better-auth/better-auth/security/advisories/GHSA-9h47-pqcx-hjr4 cve-icon
https://www.vulncheck.com/advisories/better-auth-before-insecure-cryptographic-defaults-via-oidcprovider cve-icon
History

Sat, 01 Aug 2026 12:45:00 +0000

Type Values Removed Values Added
Description better-auth versions before 1.6.11 contain insecure cryptographic defaults in the oidcProvider and mcp plugins that advertise the none algorithm and accept plain PKCE by default. Attackers can exploit algorithm negotiation to accept unsigned tokens or intercept authorization codes when PKCE plain is used instead of the required S256 method.
Title better-auth before 1.6.11 Insecure Cryptographic Defaults via oidcProvider
First Time appeared Better-auth
Better-auth better-auth\/oauth-provider
Weaknesses CWE-327
CPEs cpe:2.3:a:better-auth:better-auth\/oauth-provider:*:*:*:*:*:node.js:*:*
Vendors & Products Better-auth
Better-auth better-auth\/oauth-provider
References
Metrics cvssV3_1

{'score': 8.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N'}

cvssV4_0

{'score': 9.4, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-08-01T12:22:18.271Z

Reserved: 2026-07-29T13:07:47.016Z

Link: CVE-2026-67336

cve-icon Vulnrichment

No data.

cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses