CVE-2026-67335 PUBLISHED

better-auth before 1.6.2 OAuth State Validation Bypass

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

better-auth versions before 1.6.2 fail to validate the OAuth state parameter against the stored nonce when using cookie-backed state storage without PKCE. Attackers can forge the state parameter and supply an attacker-controlled authorization code to create authenticated sessions bound to the attacker's external identity or persistently link attacker accounts to victim profiles.

CVSS Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS Score: 6

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

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
CVSS Score: 5.3

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

CVSS 3.1

Product Status

Vendor	better-auth
Product	better-auth
Versions	Default: unaffected affected from 0 to 1.6.2 (excl.) Version 1.6.2 is unaffected

CVE-2026-67335 PUBLISHED

better-auth before 1.6.2 OAuth State Validation Bypass

Metrics

Product Status

Credits

References

Problem Types