Z/IP Gateway Use of Uninitialized PRNG when Generating S0 Encryption Key

published 2023-12-14 2 y ago modified 2026-06-17 4 mo ago also EUVD-2023-54344

cvss: 6.4; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits: 0; none known

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.

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 17 mo ago (2025-05-21)

Exploit prediction

0.53% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	6.4	CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

silabs.com Z/IP Gateway SDK

Classification

Weakness

CWE-1279 Cryptographic Operations are Run Before Supporting Units are Ready
CWE-908 Use of Uninitialized Resource

References

siliconlabs.lightning.force.com /sfc/servlet.shepherd/document/download/0698Y00000buWj0QAE?operationContext=S1
vendor-advisory, permissions-required
github.com /SiliconLabs/gecko_sdk
third-party-advisory

Sources

CVE List CVE-2023-4489
NVD CVE-2023-4489

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary