CVE-2026-92697 in FastNetMon
Summary
by MITRE • 11/06/2026
FastNetMon is a high-performance DDoS detector and sensor. In version 1.2.9 and earlier, the NetFlow v9 collector calls strlen() on an attacker-controlled interface-description field without bounding the scan to the field’s declared length. Although fields longer than 128 bytes are excluded from this operation, an accepted field without a null terminator can cause reads beyond the field and packet buffer. An unauthenticated remote attacker who can send crafted UDP packets to the collector can trigger an out-of-bounds read and potentially crash the process, causing denial of service. No fixed release is available as of this review.
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Analysis
by VulDB Data Team • 11/06/2026
FastNetMon serves as a high-performance distributed denial of service detector and sensor, relying heavily on network flow data for traffic analysis and anomaly detection. The vulnerability identified in versions 1.2.9 and earlier resides within the NetFlow v9 collector component, which is responsible for parsing incoming flow records to extract metadata about network communications. Specifically, this flaw affects the handling of the interface-description field during the processing of NetFlow version nine packets. When the system receives a UDP packet containing such data, it attempts to determine the length of the string stored in the interface description using standard C library functions without adequate validation against the declared boundaries of the buffer allocated for that specific field.
The core technical flaw is an out-of-bounds read caused by improper input validation and memory management practices. The application invokes strlen() on a user-controlled interface-description field to determine its length, but fails to ensure that the string is null-terminated or bounded by the maximum expected size of twelve8 bytes. While there is a check in place to exclude fields exceeding one hundred twenty-eight bytes from this specific operation, an attacker can craft a packet where the field is within the acceptable byte limit yet lacks a terminating null character. Consequently, strlen() continues scanning memory beyond the allocated buffer boundaries until it encounters a zero byte elsewhere in the process's address space or triggers a segmentation fault due to accessing unmapped memory regions. This behavior constitutes a classic out-of-bounds read vulnerability, allowing an unauthenticated remote attacker who can send crafted UDP packets to trigger arbitrary code execution conditions or, more commonly, cause the application process to crash.
From an operational perspective, this vulnerability presents a significant denial of service risk for organizations relying on FastNetMon for network security monitoring. Since NetFlow collection is typically performed over UDP and often does not require authentication in many deployment configurations, any host with network access to the collector can exploit this flaw. A successful exploitation results in the termination of the FastNetMon process, leading to an immediate loss of visibility into network traffic patterns. This disruption prevents the system from detecting ongoing attacks or monitoring baseline behavior, effectively blinding the security infrastructure during a critical period. The lack of a fixed release as of the review date exacerbates this risk, leaving affected systems exposed until vendors provide a patched version that implements proper bounds checking and string termination validation.
This vulnerability aligns with Common Weakness Enumeration CWE-125, which describes out-of-bounds read conditions resulting from insufficient boundary checks on input data. It also relates to CWE-787, as the improper access can lead to memory corruption or crashes depending on the specific memory layout at runtime. In terms of adversary tactics, this exploit maps to MITRE ATT&CK technique T1498, specifically Network Denial of Service via resource exhaustion through application crashes. Mitigation strategies for affected environments include deploying network-level access control lists to restrict UDP traffic destined for port 2055 or other NetFlow collection ports to only trusted management subnets. Additionally, implementing deep packet inspection at the perimeter can help identify and drop malformed flow records that lack proper null terminators before they reach the vulnerable application layer. Organizations should also consider enabling core dump analysis capabilities to better understand crash contexts if exploitation occurs while awaiting a vendor patch.