Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.1, Authlib's OctKey.import_key() and HMAC signing and verification path accept zero-length key material. If an application's secret lookup can return an empty string or empty bytes, a remote attacker can compute the deterministic HS256, HS384, or HS512 signature for arbitrary token claims and have Authlib treat the token as authentic.
This issue is fixed in version 1.9.1.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption
CVSS Vector v3.1
Weakness Type (CWE)
References 3
https://github.com/authlib/authlib/commit/4ff30db442c70e29486e1982cb0ad37c037f5…
security-advisories@github.com
https://github.com/authlib/authlib/releases/tag/v1.9.1
security-advisories@github.com
https://github.com/authlib/authlib/security/advisories/GHSA-8m4g-j4wp-wgcg
security-advisories@github.com