CVE-2025-40891: HTML injection in in Time Machine functionality in Guardian/CMC before 25.5.0

Severity: medium (CVSS 4.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-18 · updated 2026-09-30
Weakness: CWE-79

Description

A Stored HTML Injection vulnerability was discovered in the Time Machine Snapshot Diff functionality due to improper validation of network traffic data. An unauthenticated attacker can send specially crafted network packets at two different times to inject HTML tags into asset attributes across two snapshots. Exploitation requires a victim to use the Time Machine Snapshot Diff feature on those specific snapshots and perform specific GUI actions, at which point the injected HTML renders in their browser, enabling phishing and open redirect attacks. Full XSS exploitation is prevented by input validation and Content Security Policy. Attack complexity is high due to multiple required conditions.

Affected products

Nozomi Networks CMC: before 25.5.0 — fixed in 25.5.0
Nozomi Networks Guardian: before 25.5.0 — fixed in 25.5.0

How to fix

Upgrade to a fixed version: Nozomi Networks CMC 25.5.0; Nozomi Networks Guardian 25.5.0. Check the vendor advisory for mitigations.

References

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