CVE-2026-33544

Tinyauth has OAuth account confusion via shared mutable state on singleton service instances

HIGH
7.7
CVSS Score
Published: April 2, 2026 at 03:00 PM UTC
Updated: June 17, 2026 at 10:37 AM UTC
2 products affected across 2 vendorsTinyauthTinyauth

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Severity
HIGH7.7
Exploit prediction
EPSS 0.3%
SSVC
PoC

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 5.0.5
v < 5.0.5
Affected range stops below 5.0.5, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (3)

x_refsource_CONFIRMExploitMitigationVendor Advisory
Source: cverecord
https://github.com/steveiliop56/tinyauth/security/advisories/GHSA-9q5m-jfc4-wc92
x_refsource_MISCProductRelease Notes
Source: cverecord
https://github.com/steveiliop56/tinyauth/releases/tag/v5.0.5

SSVC — Action Prioritization

SSVCPoCNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.7HIGHGitHub_M
Attack Vector
NETWORK
Complexity
HIGH
Privileges
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-362

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