CyberSecBulletin
CVE-2026-66279NVD status: Awaiting Analysis

Connect SDK: Improper Verification of Source of a Communication Channel

Published Updated By the CyberSecBulletin desk

CVE-2026-66279 is a high-severity improper verification of source of a communication channel vulnerability in Connect SDK from Silicon Labs, with a CVSS 4.0 base score of 7.2 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. Affected Connect SDK versions: 4.0.0 through 4.3.1; 3.7.7 and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.24% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of Connect SDK you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
Silicon LabsConnect SDK4.0.0 through 4.3.1; 3.7.7 and earlierNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
AdjacentThe attacker must be on the same local network segment.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Attack requirements
NoneThe attack does not depend on a particular deployment or configuration.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Confidentiality (vulnerable system)
NoneNo loss of confidentiality on the vulnerable system.
Integrity (vulnerable system)
HighSerious loss of integrity on the vulnerable system.
Availability (vulnerable system)
HighSerious loss of availability on the vulnerable system.
Confidentiality (other systems)
NoneNo loss of confidentiality on systems beyond the vulnerable one.
Integrity (other systems)
NoneNo loss of integrity on systems beyond the vulnerable one.
Availability (other systems)
NoneNo loss of availability on systems beyond the vulnerable one.

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. Scored by CNA (silabs.com).

Official description

In Connect SDK 4.3.1 and earlier and Flex SDK 3.7.7 and earlier, a message with invalid security settings may bypass authentication resulting in network disruption. This vulnerability does not allow an attacker to gain the Network Key or otherwise break confidentiality.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Verification of Source of a Communication Channel

The product establishes a communication channel to handle an incoming request that has been initiated by an actor, but it does not properly verify that the request is coming from the expected origin.

How developers prevent this class of flaw

  • Use a mechanism that can validate the identity of the source, such as a certificate, and validate the integrity of data to ensure that it cannot be modified in transit using an Adversary-in-the-Middle (AITM) attack. When designing functionality of actions in the URL scheme, consider whether the action should be accessible to all mobile applications, or if an allowlist of applications to interface with is appropriate.

More Improper Verification of Source of a Communication Channel vulnerabilities (CWE-940)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Improper Verification of Source of a Communication Channel vulnerabilities

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