CVE-2026-33923 PUBLISHED

Update bundle signature bypass in Guardian/CMC before 26.4.0

Assigner: Nozomi
Reserved: 24.03.2026 Published: 29.10.2026 Updated: 29.10.2026

A signature verification vulnerability was discovered in the update installation functionality due to inconsistent validation of the update bundle contents. An attacker with administrative privileges can remotely supply a crafted update bundle that passes signature verification but runs an unsigned script when the bundle is installed. The script runs with root privileges, allowing the attacker to read or modify sensitive data, change the appliance configuration, or shut down the appliance.

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS Score: 7.5

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	None
Attack Requirements	Present	Availability	High	Availability	None
Privileges Required	High
User Interaction	None

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 7.2

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	High	Integrity Impact	High
User Interaction	None	Availability Impact	High

CVSS 3.1

Product Status

Vendor	Nozomi Networks
Product	Guardian
Versions	Default: unaffected affected from 0 to 26.4.0 (excl.)

Vendor	Nozomi Networks
Product	CMC
Versions	Default: unaffected affected from 0 to 26.4.0 (excl.)

Workarounds

Install update bundles only when they come from trusted Nozomi Networks sources.

Solutions

Upgrade to v26.4.0 or later.

Credits

This issue was found by Andrea Palanca of Nozomi Networks Product Security team during an internal investigation. finder

References

https://security.nozominetworks.com/NN-2026:21-01

Problem Types

CWE-347 Improper Verification of Cryptographic Signature CWE

Impacts

CAPEC-186 Malicious Software Update