Executive brief
node-opcua is an OPC UA (OLE for Process Control Unified Architecture) server implementation used in industrial control systems and IoT applications to facilitate secure machine-to-machine communication. A missing cryptographic nonce verification in the password authentication handler allows unauthenticated attackers to bypass authentication by crafting a forged empty password or replaying captured authentication tokens across different sessions, potentially gaining unauthorized access to sensitive operational data or control functions.
Technical details
The vulnerability is a cryptographic signature verification bypass (CWE-347) in the UserNameIdentityToken authentication handler at packages/node-opcua-server/source/opcua_server.ts lines 1886–1887. After RSA-OAEP decryption of the password blob, the server reads a 4-byte length field and extracts the password without verifying that trailing bytes match the session nonce. An unauthenticated attacker can retrieve the server's public key via an unauthenticated GetEndpoints call, craft a ciphertext where the length field equals serverNonce.length (32 bytes), causing the server to extract an empty password. Additionally, because nonce binding is absent, any captured UserNameIdentityToken can be replayed in different sessions. The attack vector is network-based with high attack complexity, requiring no prior authentication. The issue is compounded by a secondary vulnerability where SecurityMode=None causes verifyClientSignature to return true unconditionally, bypassing channel-level signature verification. Patch status unknown at time of publication (2026-08-20).
Affected products
- node-opcua node-opcua <= 2.165.0
Timeline
- 2026-03-23: disclosed: Vulnerability discovery date
- 2026-07-03: advisory: GitHub advisory published
- 2026-08-20: other: GitHub Security Advisory Database updated