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CVE-2026-48684 Pavel Odintsov CVE debrief

FastNetMon Community Edition through 1.2.9 contains an out-of-bounds read vulnerability in its NetFlow v9 options template parser. The flaw exists in `process_netflow_v9_options_template()` within `src/netflow_plugin/netflow_v9_collector.cpp`. The scope parsing loop (lines 224-229) iterates using an attacker-controlled `option_scope_length` value without validating that `(zone_address + scopes_offset + sizeof(record))` remains within the flowset boundary. A similar issue affects the options field loop (lines 241-257) with `option_length`. Additionally, `option_scope_length` is not validated as a multiple of `sizeof(netflow9_template_flowset_record_t)`, permitting misaligned reads. An attacker can trigger memory reads past the end of the UDP packet buffer.

Vendor
Pavel Odintsov
Product
FastNetMon
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-26
Original CVE updated
2026-05-27
Advisory published
2026-05-26
Advisory updated
2026-05-27

Who should care

Network operations teams running FastNetMon Community Edition for DDoS detection and traffic analysis; security teams monitoring NetFlow infrastructure; organizations using open-source network telemetry collectors.

Technical summary

The vulnerability stems from insufficient bounds validation in NetFlow v9 options template parsing. Two parsing loops—scope records (lines 224-229) and option fields (lines 241-257)—use attacker-controlled length fields (`option_scope_length`, `option_length`) as iteration terminators without verifying that each record access remains within the allocated packet buffer. The `netflow9_template_flowset_record_t` structures are read at computed offsets without checking `(zone_address + offset + sizeof(record))` against flowset boundaries. Additionally, lack of alignment validation on `option_scope_length` permits misaligned memory access. This enables out-of-bounds reads from the UDP packet buffer when processing malformed NetFlow v9 options templates.

Defensive priority

medium

Recommended defensive actions

  • Upgrade FastNetMon Community Edition to a version newer than 1.2.9 when available
  • Restrict NetFlow v9 collector access to trusted network segments and authorized flow exporters
  • Implement network segmentation to limit exposure of NetFlow collection infrastructure
  • Monitor for anomalous NetFlow v9 template packets with unusual option_scope_length or option_length values
  • Review and validate NetFlow v9 packet sizes against RFC 3954 specifications at ingestion points

Evidence notes

Vulnerability description sourced from official CVE record and NVD entry. Technical details reference specific source file paths and line numbers. Vendor attribution based on GitHub repository references in source metadata.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-48684 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-48684

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-48684 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-48684

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.