node-opcua: Missing nonce verification in UserNameIdentityToken authentication

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

14 Sep 2026 16:07:50 UTC

Source modified

14 Sep 2026 16:39:35 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 7.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

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.

Source published

Sep 14, 2026, 4:07:50 PM (timezone not stated)

Source modified

Sep 14, 2026, 4:39:35 PM (timezone not stated)

Observed here

11 Nov 2026 13:58:59 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 7.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

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.

Source published

14 Sep 2026 17:17:46 UTC

Source modified

30 Sep 2026 19:38:27 UTC

Observed here

25 Oct 2026 13:17:22 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

**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

Source published

20 Aug 2026 18:35:33 UTC

Source modified

20 Aug 2026 18:48:09 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

Publisher rating · HIGH