Bug 2567951 (CVE-2026-93424)

Summary: CVE-2026-93424 fastnetmon: FastNetMon: Denial of Service via race condition in NetFlow template processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in FastNetMon. An unauthenticated remote attacker with access to the NetFlow or IPFIX listening ports can trigger a race condition during concurrent template updates and traffic processing. This issue causes the application to access memory after it has been freed (a use-after-free condition), leading to an application crash and resulting in a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-11-05 22:41:32 UTC 
FastNetMon is a high-performance DDoS detector and sensor. In version 1.2.9 and earlier, peer_find_template() in src/netflow_plugin/netflow_collector.cpp and src/netflow_plugin/netflow_v9_collector.cpp returns a pointer into global_netflow9_templates after releasing the cache mutex. On deployments with at least two entries in netflow_ports, concurrent template redefinition and data-flowset processing can let add_update_peer_template() reassign the template and free its records vector while another listener dereferences the escaped pointer. An unauthenticated sender that can reach both NetFlow/IPFIX listener ports can trigger a heap-use-after-free and reliably crash FastNetMon. No fixed release is available as of this review.