Authentication bypass via unsigned OIDC token acceptance
Published Mar 30, 2026 · Updated Mar 30, 2026
Authentication bypass in OpenOlat 10.5.4 through 20.2.4 allows remote attackers to impersonate any user via a forged OIDC token. JSONWebToken.parse() discards the JWT signature, while both getAccessToken() implementations validate claims without verifying the token against the identity provider's JWKS. Exploitation requires an enabled OIDC implicit flow and attacker-obtained state and nonce values, after which the forged subject can establish a session as any user, including an administrator.
Summary
What happened
Authentication bypass in OpenOlat 10.5.4 through 20.2.4 allows remote attackers to impersonate any user via a forged OIDC token. JSONWebToken.parse() discards the JWT signature, while both getAccessToken() implementations validate claims without verifying the token against the identity provider's JWKS. Exploitation requires an enabled OIDC implicit flow and attacker-obtained state and nonce values, after which the forged subject can establish a session as any user, including an administrator.
The record
- CVE
- CVE-2026-31946
- Published
- Mar 30, 2026
- Updated
- Mar 30, 2026
- Vendor
- frentix GmbH
- Product
- OpenOlat
- Classifications
- CWE-287, CWE-347, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 30, 2026CVE publishedPublication date reported by the CVE source.
- Mar 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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 10.5.4, < 20.2.5
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
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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