title: Disallow replay of `private_key_jwt` by blacklisting JTIs in Hydra
description: In Hydra (an OAuth2 Server and OpenID Certified™ OpenID Connect Provider written in Go), before version 1.4.0+oryOS.17, when using client authentication method 'private_key_jwt' [1], OpenId specification says the following about assertion `jti`: "A unique identifier for the token, which can be used to prevent reuse of the token. These tokens MUST only be used once, unless conditions for reuse were negotiated between the parties". Hydra does not check the uniqueness of this `jti` value. Exploiting this vulnerability is somewhat difficult because: - TLS protects against MITM which makes it difficult to intercept valid tokens for replay attacks - The expiry time of the JWT gives only a short window of opportunity where it could be replayed This has been patched in version v1.4.0+oryOS.17
problem types: CWE-294: Authentication Bypass by Capture-replay
affected:
{
product: hydra
vendor: ory
versions:
status: affected, version: < 1.4.0+oryOS.17
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: NONE
baseScore: 5.8
baseSeverity: MEDIUM
confidentialityImpact: HIGH
integrityImpact: NONE
privilegesRequired: LOW
scope: CHANGED
userInteraction: REQUIRED
vectorString: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N
version: 3.1
]