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HIGH severity

CVE-2026-54155

HIGH

CVE-2026-54155 is a high-severity (CVSS 7.7) vulnerability in node-opcua. O3 Security confirms whether CVE-2026-54155 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

node-opcua missing nonce verification in UserNameIdentityToken authentication

Published
Aug 20, 2026
Updated
Aug 20, 2026
Affected
1 pkg
Patched
None yet
Exploits
None indexed
Exploitation data as of Aug 20, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

115other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
node-opcuanpm
42Kdownloads / week

Description

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

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 unconditionally (security_policy.ts:697-700), bypassing the channel-level signature check entirely.

Proof of Concept (logic, no exploit code)

1. GetEndpoints (unauthenticated) → retrieve server public key and RSA token policy
2. OpenSecureChannel (SecurityMode=None)
3. CreateSession
4. Craft plaintext: [0x20, 0x00, 0x00, 0x00]  (readUInt32LE = 32 = serverNonce.length)
5. RSA-OAEP encrypt with server public key → 256-byte ciphertext
6. ActivateSession with crafted UserNameIdentityToken
7. Server decrypts → length = 32 - 32 = 0 → password = ""
8. isValidUser(username, "") is called

Dynamically confirmed: decryption produces password = "" with no error and no nonce verification.

Suggested Fix

After decrypting the password blob, verify that buff.slice(4 + passwordLength) equals session.nonce before extracting the password. Reject the token if verification fails.

I am following a 90-day responsible disclosure policy. I am happy to provide additional technical details under embargo. Please confirm receipt at your earliest convenience.

Reporter: Stanley Tobias Discovery date: 2026-03-23

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
📦npmnode-opcuaall versionsNo fix

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for node-opcua. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Remediation status

    No patched version of node-opcua has shipped for CVE-2026-54155 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  3. Mitigate without a patch

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether CVE-2026-54155 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-54155. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

**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 --- **Root Cause** In `packages/node-opcua-server/source/opcua_server.ts` at line 1886-1887, after RSA-OAEP decrypting the
O3 Security · Impact-Aware SCA

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