CVE-2024-56072

What it actually does

The sFlow v5 plugin in FastNetMon Community Edition crashes the application when processing a crafted packet that specifies many sFlow samples.

Why it matters to the business

Network monitoring becomes unavailable, leading to potential delays in detecting traffic anomalies or security incidents and operational disruption for teams relying on the tool.

How an attack unfolds

An attacker sends a specially crafted sFlow v5 packet containing an excessive number of samples to an exposed FastNetMon instance, triggering an unhandled condition in the plugin that causes the entire application to crash.

How to fix it

Upgrade FastNetMon Community Edition beyond version 1.2.7. Where applicable, apply the listed package fixes such as php5 (Ubuntu:14.04:LTS) fixed in 5.5.9+dfsg-1ubuntu4.16 and php7.0 (Ubuntu:16.04:LTS) fixed in 7.0.4-7ubuntu2.1.

How to confirm the fix worked

Confirm the running FastNetMon version is newer than 1.2.7, test the sFlow v5 plugin with sample traffic, and verify the process remains stable under load.

Typical attack path

1. Locate an internet-facing or internally reachable FastNetMon deployment listening for sFlow v5 traffic
2. Craft a malicious sFlow v5 packet that declares a large number of samples
3. Transmit the packet to the target to induce the crash

How to detect it

Review application crash logs and sFlow-related error entries around the time of any outage; look for repeated malformed sFlow packet patterns in captured traffic.

What your security team should do

• Prioritize upgrade of FastNetMon Community Edition to a fixed release
• Restrict sFlow listener exposure to trusted sources only via network controls
• Monitor EPSS trend for any increase indicating rising exploit interest