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EUVD-2026-368019

2026-10-07T13:09:59.533537+00:00

EUVD-2026-368019

fkie_cve-2026-54155

2026-10-07T13:09:59.533589+00:00

node-opcua is an OPC UA implementation for TypeScript and Node.js. Prior to 2.166.0, the UserNameIdentityToken authentication handler in packages/node-opcua-server/source/opcua_server.ts decrypts an RSA-OAEP password blob but does not verify that the trailing bytes match the current session serverNonce. An unauthenticated remote attacker can obtain the server public key through GetEndpoints and forge a blob whose little-endian length produces an empty password passed to isValidUser, compromising accounts that accept an empty password. Missing nonce binding also allows a captured UserNameIdentityToken ciphertext to be replayed in another session, and SecurityMode=None removes the separate client-signature safeguard. This issue is fixed in version 2.166.0.

GHSA-mq36-523m-x7vv — node-opcua missing nonce verification in UserNameIdentityToken authentication

2026-10-07T13:09:59.533646+00:00

Affected: npm: node-opcua

**Summary** A missing nonce verification in the UserNameIdentityToken authentication handler allows an unauthenticated remote attacker to forge a password token that extracts as an empty string, and to replay captured authentication tokens across sessions.

**Affected versions:** <= 2.165.0 **Tested version:** 2.165.0 **CVSS Score:** 8.1 (High) **CVSS Vector:** CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L **CWE:** CWE-347 Improper Verification of Cryptographic Signature

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**Root Cause**

In `packages/node-opcua-server/source/opcua_server.ts` at line 1886-1887, after RSA-OAEP decrypting the UserNameIdentityToken password blob, the server reads a 4-byte little-endian length field and extracts `buff[4 : 4+length]` as the password. It never verifies that the trailing bytes equal `session.nonce`.

This has two consequences:

1. **Forged empty password:** An attacker who retrieves the server's public key via an unauthenticated `GetEndpoints` call can craft a token where the 4-byte length field equals `serverNonce.length` (32). The server computes `length = 32 - 32 = 0` and calls `isValidUser(username, "")`. Any account that accepts an empty password is compromised.

2. **Unconditional replay attack:** Because nonce binding is structurally absent, any captured UserNameIdentityToken ciphertext can be replayed in a different session unconditionally.

The impact is compounded by a second issue: when the channel uses `SecurityMode=None`, `verifyClientSignature` returns `true` uncon…