CVE-2026-54155

HIGHPre-NVD 7.77.7—
EchelonGraph scoreHIGH confidence

Score 7.7 from GitHub Security Advisory (severity: HIGH) published 2026-08-20. the CNA's CVSS baseline 7.7; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:github_m, ghsa
7.7EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 7.7Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

node-opcua missing nonce verification in UserNameIdentityToken authentication

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:

  • 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.
  • 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

  • OpenSecureChannel (SecurityMode=None)
    • 

  • CreateSession
    • 

  • Craft plaintext: [0x20, 0x00, 0x00, 0x00]  (readUInt32LE = 32 = serverNonce.length)
    • 

  • RSA-OAEP encrypt with server public key → 256-byte ciphertext
    • 

  • ActivateSession with crafted UserNameIdentityToken
    • 

  • Server decrypts → length = 32 - 32 = 0 → password = ""
    • 

  • 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

CVSS v3
7.7
EG Score
7.7(high)
EG Risk
39(Track)
EG Risk 39/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity77% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
—
EPSS %ILE
—
KEV
Not listed

Published

August 20, 2026

Last Modified

August 20, 2026

Vendor Advisories for CVE-2026-54155(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
npmnode-opcua—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 3× in last 7d / 3× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-21 05:35 UTCGHSA enrichment
  2. 2026-08-20 18:42 UTCEG score recompute
  3. 2026-08-20 18:42 UTCGHSA enrichment

Frequently asked(4)

What is CVE-2026-54155?
CVE-2026-54155 is a high vulnerability published on August 20, 2026. node-opcua missing nonce verification in UserNameIdentityToken authentication 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…
When was CVE-2026-54155 disclosed?
CVE-2026-54155 was first published in the National Vulnerability Database on August 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-54155?
CVE-2026-54155 has a CVSS v4.0 base score of 7.7 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-54155?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54155, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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