better-auth versions before 1.6.11 contain insecure cryptographic defaults in the oidcProvider and mcp plugins that advertise the none algorithm and… (CVE-2026-67336)
better-auth versions before 1.6.11 have insecure cryptographic defaults in the oidcProvider and mcp plugins. These defaults advertise the 'none' algorithm and accept plain PKCE by default, which can be exploited by attackers to accept unsigned tokens or intercept authorization codes. This vulnerability affects the security of token validation and authorization code exchange.
AI Analysis
Technical Summary
The vulnerability in better-auth prior to version 1.6.11 involves insecure cryptographic defaults in the oidcProvider and mcp plugins. Specifically, these plugins advertise the 'none' algorithm for token signing and accept plain PKCE (Proof Key for Code Exchange) instead of enforcing the more secure S256 method. This allows attackers to exploit algorithm negotiation to accept unsigned tokens or intercept authorization codes during the PKCE plain method usage, undermining the integrity and confidentiality of authentication flows.
Potential Impact
Successful exploitation can lead to acceptance of unsigned tokens, allowing attackers to bypass token signature verification, and interception of authorization codes when plain PKCE is used, potentially leading to unauthorized access and compromise of user sessions. The vulnerability has a CVSS score of 8.7 (critical), indicating high impact on confidentiality and integrity without affecting availability.
Mitigation Recommendations
A fix is available in better-auth version 1.6.11 that addresses these insecure cryptographic defaults. Users should upgrade to version 1.6.11 or later to mitigate this vulnerability. No other mitigation guidance is provided or required beyond applying the official fix.
better-auth versions before 1.6.11 contain insecure cryptographic defaults in the oidcProvider and mcp plugins that advertise the none algorithm and… (CVE-2026-67336)
Description
better-auth versions before 1.6.11 have insecure cryptographic defaults in the oidcProvider and mcp plugins. These defaults advertise the 'none' algorithm and accept plain PKCE by default, which can be exploited by attackers to accept unsigned tokens or intercept authorization codes. This vulnerability affects the security of token validation and authorization code exchange.
CVSS v3.1
Score 8.7high
Affected software
pkg:github/better-auth/better-authRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in better-auth prior to version 1.6.11 involves insecure cryptographic defaults in the oidcProvider and mcp plugins. Specifically, these plugins advertise the 'none' algorithm for token signing and accept plain PKCE (Proof Key for Code Exchange) instead of enforcing the more secure S256 method. This allows attackers to exploit algorithm negotiation to accept unsigned tokens or intercept authorization codes during the PKCE plain method usage, undermining the integrity and confidentiality of authentication flows.
Potential Impact
Successful exploitation can lead to acceptance of unsigned tokens, allowing attackers to bypass token signature verification, and interception of authorization codes when plain PKCE is used, potentially leading to unauthorized access and compromise of user sessions. The vulnerability has a CVSS score of 8.7 (critical), indicating high impact on confidentiality and integrity without affecting availability.
Mitigation Recommendations
A fix is available in better-auth version 1.6.11 that addresses these insecure cryptographic defaults. Users should upgrade to version 1.6.11 or later to mitigate this vulnerability. No other mitigation guidance is provided or required beyond applying the official fix.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-mw34-3w2r-wp9p
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-67336"]
- Ecosystems
- []
- Database Specific Severity
- CRITICAL
- Cvss Version
- 3.1
Threat ID: 6a6e6290bf32cb7a344f5e38
Added to database: 08/01/2026, 21:18:08 UTC
Last enriched: 08/01/2026, 21:20:00 UTC
Last updated: 08/02/2026, 01:04:32 UTC
Views: 16
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