How severe is CVE-2026-33544?

CVE-2026-33544 has a CVSS 3.x base score of 7.7, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-33544 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-33544?

CVE-2026-33544 affects Tinyauth. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-33544?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-33544 have an EU (EUVD) identifier?

Yes. CVE-2026-33544 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18254.

When was CVE-2026-33544 published?

CVE-2026-33544 was published on 2026-04-02 and last updated on 2026-06-17.

CVE-2026-33544

CVE-2026-33544 is a high-severity vulnerability in Tinyauth with a CVSS 3.x base score of 7.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-362.

Key facts

Severity: High (CVSS 3.x base score 7.7)
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18254
Weakness: CWE-362
Affected product: Tinyauth
Published: 2026-04-02
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-33544?: CVE-2026-33544 has a CVSS 3.x base score of 7.7, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-33544 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33544?: CVE-2026-33544 affects Tinyauth. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-33544?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-33544 have an EU (EUVD) identifier?: Yes. CVE-2026-33544 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18254.
When was CVE-2026-33544 published?: CVE-2026-33544 was published on 2026-04-02 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:tinyauth:tinyauth:*:*:*:*:*:*:*:*

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