Horizon Alert
Summary of the vulnerability and why it matters
A vulnerability in the joserfc Python library could allow an attacker to bypass signature verification for certain types of JSON Web Signatures, potentially leading to the acceptance of unauthenticated data as legitimate. This issue is specific to the General JSON Serialization path and does not affect other JOSE processing methods. The main concern is confirming relevance and exposure within your applications that utilize this library for handling signed data.
- Unauthenticated data can be accepted as legitimate.
- Library used for signing and encryption data.
- Confirm relevance and exposure within applications.
Attack Path
How an attacker could exploit the issue
An attacker can send a specially crafted JSON Web Signature (JWS) containing an empty signatures array to an application using the joserfc library. The library will incorrectly process this malformed signature as valid, allowing the attacker to bypass authentication and potentially inject arbitrary content that the application will trust.
- No authentication required.
- JWS General JSON Serialization with empty signatures.
- Application treats unverified payload as authentic.
Live Threat
Current exploitation, exposure, and threat context
When supported by the advisory, applications using `joserfc` for JWS General JSON Serialization might incorrectly authenticate untrusted payloads if an empty signature array is provided. This could allow an attacker to supply arbitrary data that the application then treats as legitimate.
- JWS General JSON Serialization data.
- Empty signature array provided.
- Untrusted data authenticated as valid.
Operational Fix
Recommended remediation, mitigation, and detection steps
The joserfc Python library's vulnerability in handling empty signature arrays affects applications that use its General JSON Serialization path for JWS deserialization. The first step is to identify all applications consuming this library, determine their exposure and criticality, and locate the accountable application owners. Once identified, a targeted remediation plan can be developed based on risk.
- Confirm applications using this library.
- Verify General JSON Serialization usage.
- Plan remediation with application owners.
