CVE-2026-67336 PUBLISHED

better-auth before 1.6.11 Insecure Cryptographic Defaults via oidcProvider

Assigner: VulnCheck
Reserved: 29.07.2026 Published: 01.08.2026 Updated: 01.08.2026

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.

CVSS 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
CVSS Score: 9.4

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	High
Attack Complexity	High	Integrity	High	Integrity	High
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
CVSS Score: 8.7

Attack Vector	Network	Scope	Changed
Attack Complexity	High	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	High
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	better-auth
Product	better-auth
Versions	Default: unaffected affected from 0 to 1.6.11 (excl.) Version 1.6.11 is unaffected

CVE-2026-67336 PUBLISHED

better-auth before 1.6.11 Insecure Cryptographic Defaults via oidcProvider

Metrics

Product Status

Credits

References

Problem Types