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

CVE-2026-33544 · Severity: high · CVSS 7.7 · Published 2026-04-02

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.

Technologies: github.com/steveiliop56/tinyauth (Go). Vendors: Go.

Quick answers

Is CVE-2026-33544 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-33544 being exploited in the wild.
How severe is CVE-2026-33544?
High severity, with a CVSS score of 7.7, published 2 April 2026.
Which products and versions are affected?
github.com/steveiliop56/tinyauth (Go) SEMVER:introduced=0,fixed=1.0.1-0.20260401140714-fc1d4f2082a5.
Is there a fix for CVE-2026-33544?
Yes. github.com/steveiliop56/tinyauth (Go): upgrade to 1.0.1-0.20260401140714-fc1d4f2082a5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-33544?
Check whether you run github.com/steveiliop56/tinyauth (Go) or Tinyauth at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/steveiliop56/tinyauth (Go): upgrade to 1.0.1-0.20260401140714-fc1d4f2082a5 or later
    go get github.com/steveiliop56/tinyauth@v1.0.1-0.20260401140714-fc1d4f2082a5

Affected products

  • github.com/steveiliop56/tinyauth (Go) SEMVER:introduced=0,fixed=1.0.1-0.20260401140714-fc1d4f2082a5
  • Tinyauth

Identifiers

  • CVE-2026-33544
  • GHSA-9q5m-jfc4-wc92
  • GO-2026-5296

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