CVE-2026-48684
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedFastNetMon 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFastNetMon Community Edition before 1.2.9 has an out-of-bounds read vulnerability in the NetFlow v9 options template parser. The process_netflow_v9_options_template() function iterates through scope and option fields using attacker-controlled length values without validating that the calculated offsets stay within the flowset buffer, allowing reads past the end of the UDP packet.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 1.2.9CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify if FastNetMon is installedCheck for FastNetMon binary: run 'which fastnetmon' or look for /usr/bin/fastnetmon, /opt/fastnetmon/ directory, or check if process 'fastnetmon' is runningAffected if FastNetMon binary or process is found on the system
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Determine installed FastNetMon versionRun 'fastnetmon --version' or check version file if present in installation directoryAffected if Version is 1.2.9 or lower (any version through 1.2.9 is affected)
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Verify NetFlow v9 collection is enabledCheck FastNetMon configuration file (typically /etc/fastnetmon.conf or /opt/fastnetmon/fastnetmon.conf) for 'netflow' or 'flow_collector' settings, and look for 'process_netflow_v9' or similar optionsAffected if NetFlow v9 processing is enabled in the configuration
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Confirm UDP listener is active for NetFlowCheck listening UDP ports: run 'netstat -ulnp | grep 2055' or 'ss -ulnp | grep 2055' (default NetFlow port), also check config for custom portAffected if UDP port for NetFlow (default 2055 or configured port) is open and listening
System is affected if FastNetMon Community Edition version 1.2.9 or lower is installed with NetFlow v9 collection enabled and a UDP listener configured to receive NetFlow packets.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataImplement bounds checking to validate that (zone_address + scopes_offset + sizeof(record)) remains within the flowset buffer, add similar validation for the options field loop, and ensure option_scope_length is a multiple of sizeof(netflow9_template_flowset_record_t) before processing.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-48684 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-48684 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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