CVE-2020-5300: Disallow replay of `private_key_jwt` by blacklisting JTIs in Hydra

Vulnerability summary

CVE-2020-5300 is a medium (CVSS 5.8) Authentication Bypass by Capture-replay vulnerability in ory hydra. EPSS estimates a 1.03% chance of exploitation in the next 30 days, higher than 63.6% of scored vulnerabilities.

Timeline

1. 06-04-2020
   PublishedVulnerability first disclosed.
2. 04-08-2024
   Last modifiedVulnerability information updated.

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

• CWE-294Authentication Bypass by Capture-replayA capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes).