OIDC impersonation via unverified ID token claims
Published Sep 30, 2026 · Updated Sep 30, 2026
Authentication bypass in Quenary Tugtainer before 1.31.3 allows remote attackers to impersonate users through forged OIDC ID tokens. During OIDC login, auth_oidc_provider.py calls jwt.get_unverified_claims() on the provider token and uses its identity claims as the session user without validating the signature, audience, issuer, or expiry. Exploitation requires an on-path position or control of the configured identity provider or token endpoint; a forged token then yields a session for the chosen identity.
Summary
What happened
Authentication bypass in Quenary Tugtainer before 1.31.3 allows remote attackers to impersonate users through forged OIDC ID tokens. During OIDC login, auth_oidc_provider.py calls jwt.get_unverified_claims() on the provider token and uses its identity claims as the session user without validating the signature, audience, issuer, or expiry. Exploitation requires an on-path position or control of the configured identity provider or token endpoint; a forged token then yields a session for the chosen identity.
The record
- CVE
- CVE-2026-87004
- Published
- Sep 30, 2026
- Updated
- Sep 30, 2026
- Vendor
- Quenary
- Product
- Tugtainer
- Classifications
- CWE-347, T1606
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 30, 2026CVE publishedPublication date reported by the CVE source.
- Sep 30, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=< 1.31.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
- Forged OIDC ID token proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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