Eclipse ThreadX NetX Duo: Out-of-bounds write in TLS 1.3 handshake cache
Summary
NetX Duo, the TCP/IP stack of Eclipse ThreadX used in embedded and IoT devices, has an out-of-bounds write in its TLS 1.3 handshake message cache in all versions up to and including 6.5.1.202602. A malicious or compromised server can send an oversized HelloRetryRequest cookie, which makes a TLS 1.3 client write past a fixed 500-byte buffer into the TLS session control block before certificate authentication completes. The outcome ranges from a crash to corruption of data the handshake uses; no server certificate is needed. Only builds with NX_SECURE_TLS_ENABLE_TLS_1_3 enabled are affected, and the CVSS score is 9.3 in the CNA record but 9.8 in the vendor advisory.
Affected
- Eclipse ThreadX NetX Duo, all versions up to and including 6.5.1.202602
- Affected only when acting as a TLS 1.3 client (NX_SECURE_TLS_ENABLE_TLS_1_3 defined, off by default) with ECC ciphersuites
Fixed in
- NetX Duo 6.5.2.202603
- Whether later builds such as 6.5.2.202603a are also fixed is not confirmed; check the vendor advisory before relying on them
Workaround
- Build without NX_SECURE_TLS_ENABLE_TLS_1_3, which avoids the HelloRetryRequest path
- No workaround exists for a build that requires TLS 1.3 as a client
Exploitation
- No known exploitation in the wild at the time of writing
- Not listed in the CISA KEV catalog; no public proof of concept found
- CISA SSVC: exploitation none, automatable yes, technical impact total
- EPSS score 0.00209 (very low)
Our recommendation
- Inventory devices and firmware that embed NetX Duo and ask vendors which version they use
- Update affected firmware to NetX Duo 6.5.2.202603 or a later version confirmed as fixed by the vendor
- Prioritise devices with TLS 1.3 client functions that connect to untrusted or third-party endpoints
- Monitor outbound TLS connections from these devices for unexpected behaviour until patched
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Eclipse GHSA-4x76-j955-qhq2 advisory github.com
- Eclipse NetX Duo release 6.5.2.202603 github.com
- OSV record CVE-2026-103416 osv.dev
- OpenCVE CVE-2026-103416 app.opencve.io
- Vulners CVE-2026-103416 vulners.com
- Threatint CVE-2026-103416 cve.threatint.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 03:06.
Original description (NVD)
Out-of-bounds write via the TLS 1.3 handshake message cache in NetX Duo in Eclipse ThreadX NetX Duo 6.5.1.202602 allows a handshake message larger than the cache writes past it and on into the rest of the session control block, which holds pointers. A malicious or compromised server can make a TLS 1.3 client produce such a message before certificate authentication completes, so no server certificate is needed to reach it.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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