Vulnerability in Steveiliop56 Tinyauth
CVE-2026-33544
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.
Vulnerability class: Race Condition
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.7 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.003 (24.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 24th percentile — 24.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: -0.000
Affected products
- Steveiliop56 Tinyauth — versions < 5.0.5
- Tinyauth
Weakness classification (CWE)
References
- github.com/steveiliop56/tinyauth/security/advisories/GHSA-9q5m-jfc4-wc92 (Exploit, Mitigation, Vendor Advisory)
- github.com/steveiliop56/tinyauth/commit/f26c2171610d5c2dfbba2edb6ccd39490e349803 (Patch)
- github.com/steveiliop56/tinyauth/releases/tag/v5.0.5 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-33544?
- CVE-2026-33544 is a high-severity vulnerability in Steveiliop56 Tinyauth, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.7/10. Published 2026-04-02.
- How severe is CVE-2026-33544?
- High severity. CVSS v3 base score is 7.7 out of 10.