Vulnerability · Published Dec 18, 2025 · Assigned by Nozomi
CVE-2025-40891HTML injection in in Time Machine functionality in Guardian/CMC before 25.5.0
Medium 4.7
In plain English
A medium-severity cross-site scripting in CMC from Nozomi Networks. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities).
Official 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 (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Nozomi Networks | Guardian | 0 – before 25.5.0 |
| Nozomi Networks | CMC | 0 – before 25.5.0 |
Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N