---
id: CVE-2026-93475
title: Out-of-bounds Write via an Unbounded RSA Modulus in NetX Secure X.509
summary: >-
  The X.509 parser in NetX Secure accepts an RSA public key of any size, but
  every signature-verification path decrypts into fixed-size buffers dimensioned
  for the `NX_CRYPTO_MAX_RSA_MODULUS_SIZE` default of 4096 bits. A certificate
  carryi…
severity: critical
cvss: 9.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'
cvssSource: cna
cwe:
  - CWE-787
  - CWE-1284
vendor: Eclipse Foundation
product: NetX Duo
affected:
  - netx_duo <= 6.5.1.202602
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-20T17:02:43.642743Z'
published: '2026-10-20'
updated: '2026-10-20'
sourceUpdated: '2026-10-20T17:02:52.372Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-93475'
references:
  - url: >-
      https://github.com/eclipse-threadx/netxduo/security/advisories/GHSA-rcv5-vfff-25gh
tags:
  - cve.org
ingestedAt: '2026-10-20T16:10:53.334Z'
---

## Overview

The X.509 parser in NetX Secure accepts an RSA public key of any size, but every signature-verification path decrypts into fixed-size buffers dimensioned for the `NX_CRYPTO_MAX_RSA_MODULUS_SIZE` default of 4096 bits. A certificate carrying a larger modulus drives an out-of-bounds write past a file-scope static during ordinary certificate-chain verification.



It is reachable pre-authentication. The issuer used for the crypto operation is looked up in the remote, peer-supplied store before the trusted store, so the attacker supplies the oversized key themselves as an intermediate in the chain they present. It triggers on a TLS or DTLS client verifying a malicious server's chain, and on a server performing client-certificate authentication.

## Affected

- `netx_duo <= 6.5.1.202602`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.