CVE-2026-48684
Analyzed Analyzed - Analysis Complete
Out-of-Bounds Read in FastNetMon Community Edition

Publication date: 2026-05-26

Last updated on: 2026-05-27

Assigner: MITRE

Description
FastNetMon Community Edition through 1.2.9 contains an out-of-bounds read in the NetFlow v9 options template parser. In process_netflow_v9_options_template() (src/netflow_plugin/netflow_v9_collector.cpp), the scope parsing loop (lines 224-229) iterates until scopes_offset reaches the attacker-controlled option_scope_length value, reading netflow9_template_flowset_record_t structures at each step. No bounds check validates that (zone_address + scopes_offset + sizeof(record)) stays within the flowset. The same issue affects the options field loop (lines 241-257) with option_length. Furthermore, option_scope_length is not validated to be a multiple of sizeof(netflow9_template_flowset_record_t), potentially causing misaligned reads. An attacker can trigger reads past the end of the UDP packet buffer.
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Meta Information
Published
2026-05-26
Last Modified
2026-05-27
Generated
2026-06-16
AI Q&A
2026-05-26
EPSS Evaluated
2026-06-14
NVD
CVE-2026-48684
EUVD
EUVD-2026-31840
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
pavel-odintsov fastnetmon to 1.2.9 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-125 The product reads data past the end, or before the beginning, of the intended buffer.
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Executive Summary

CVE-2026-48684 is a vulnerability in FastNetMon Community Edition (up to version 1.2.9) affecting the NetFlow v9 options template parser.

The issue occurs in the function process_netflow_v9_options_template(), where two loops parse length fields controlled by an attacker without proper bounds checking.

This lack of validation allows an attacker to cause out-of-bounds reads by sending a specially crafted UDP packet, leading to memory reads beyond the packet boundary.

Impact Analysis

This vulnerability can have several impacts including exposing sensitive data from memory, crashing the FastNetMon service, or causing type confusion in downstream consumers.

An attacker can exploit this by sending a single crafted UDP packet to the default NetFlow v9 port (2055), making it relatively easy to trigger.

Compliance Impact

The vulnerability in FastNetMon Community Edition allows out-of-bounds reads that can potentially expose sensitive data or cause service crashes. Such exposure or disruption could impact compliance with standards like GDPR or HIPAA, which require protection of sensitive data and system availability. However, the provided information does not explicitly discuss compliance implications or regulatory impacts.

Detection Guidance

This vulnerability can be detected by monitoring for suspicious or malformed UDP packets sent to the default NetFlow v9 port (2055), as the exploit involves a single crafted UDP packet with manipulated length fields.

You can use network packet capture and analysis tools such as tcpdump or Wireshark to capture UDP traffic on port 2055 and inspect for abnormal NetFlow v9 option templates.

  • Use tcpdump to capture UDP packets on port 2055: tcpdump -i <interface> udp port 2055 -w capture.pcap
  • Analyze the captured packets with Wireshark, focusing on NetFlow v9 option templates for irregular option_scope_length or option_length fields.

Additionally, monitoring FastNetMon logs for crashes or unusual behavior related to NetFlow v9 processing may indicate exploitation attempts.

Mitigation Strategies

Immediate mitigation steps include restricting access to the NetFlow v9 UDP port (2055) using firewall rules to block or limit incoming traffic from untrusted sources.

You can also bind the FastNetMon NetFlow v9 collector to a specific trusted network interface to reduce exposure.

If feasible, disable the NetFlow v9 collector feature in FastNetMon until a vendor fix is released.

These mitigations help prevent attackers from sending crafted UDP packets that trigger the out-of-bounds read vulnerability.

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