What’s Vulnerable › Vulnerabilities

CVE-2026-33544: Tinyauth has OAuth account confusion via shared mutable state on singleton service instances

• Severity: high (CVSS 7.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-04-02 · updated 2026-10-26
• Weakness: CWE-362

Description

Tinyauth is an authentication and authorization server. Prior to version 5.0.5, all three OAuth service implementations (GenericOAuthService, GithubOAuthService, GoogleOAuthService) store PKCE verifiers and access tokens as mutable struct fields on singleton instances shared across all concurrent requests. When two users initiate OAuth login for the same provider concurrently, a race condition between VerifyCode() and Userinfo() causes one user to receive a session with the other user's identity. This issue has been patched in version 5.0.5.

Affected products

• steveiliop56 tinyauth: before 5.0.5 — fixed in 5.0.5

How to fix

Upgrade to a fixed version: steveiliop56 tinyauth 5.0.5. Check the vendor advisory for mitigations.

References

• https://github.com/steveiliop56/tinyauth/commit/f26c2171610d5c2dfbba2edb6ccd39490e349803
• https://github.com/steveiliop56/tinyauth/releases/tag/v5.0.5
• https://github.com/steveiliop56/tinyauth/security/advisories/GHSA-9q5m-jfc4-wc92

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