---
title: "CVE-2026-66279: Connect SDK & Flex SDK - Authentication Bypass"
description: "Connect SDK <= 4.3.1 and Flex SDK <= 3.7.7 contain an authentication bypass caused by processing messages with invalid security settings, letting attackers disrupt network operations, exploit requires sending crafted messages."
url: https://panop.io/threat-heartbeat/CVE-2026-66279/
---

# CVE-2026-66279 Connect SDK & Flex SDK - Authentication Bypass

Connect SDK <= 4.3.1 and Flex SDK <= 3.7.7 contain an authentication bypass caused by processing messages with invalid security settings, letting attackers disrupt network operations, exploit requires sending crafted messages.

CVSS base score 7.2 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-66279)

## Details

Type

Authentication Bypass

Impact

Denial Of Service

CVSS vector

CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Published

22 October 2026

Updated

23 October 2026

Weakness

[CWE-940](https://cwe.mitre.org/data/definitions/940.html)

## Vendor fix

Update to versions later than Connect SDK 4.3.1 and Flex SDK 3.7.7 or latest available versions.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-66279](https://nvd.nist.gov/vuln/detail/CVE-2026-66279)
- [https://github.com/SiliconLabsSoftware/docs-security-advisories/blob/main/Advisories/500-599/A-00000588.md](https://github.com/SiliconLabsSoftware/docs-security-advisories/blob/main/Advisories/500-599/A-00000588.md)
- [https://github.com/SiliconLabsSoftware/sisdk-release/](https://github.com/SiliconLabsSoftware/sisdk-release/)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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