CVE-2023-4489: Z/IP Gateway Use of Uninitialized PRNG when Generating S0 Encryption Key

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-12-14 · updated 2026-06-17
Weakness: CWE-1279

Description

The first S0 encryption key is generated with an uninitialized PRNG in Z/IP Gateway products running Silicon Labs Z/IP Gateway SDK v7.18.3 and earlier. This makes the first S0 key generated at startup predictable, potentially allowing network key prediction and unauthorized S0 network access.

Affected products

Silicon Labs Z/IP Gateway: through 7.18.03

References

https://github.com/SiliconLabs/gecko_sdk
https://siliconlabs.lightning.force.com/sfc/servlet.shepherd/document/download/0698Y00000buWj0QAE?operationContext=S1
https://github.com/SiliconLabs/gecko_sdk
https://siliconlabs.lightning.force.com/sfc/servlet.shepherd/document/download/0698Y00000buWj0QAE?operationContext=S1

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