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CVE-2026-48690 Pavel Odintsov CVE debrief

FastNetMon Community Edition through 1.2.9 contains an integer overflow vulnerability in the packet capture buffer allocation. In src/packet_storage.hpp, the allocate_buffer() function computes memory_size_in_bytes as 'buffer_size_in_packets * (max_captured_packet_size + sizeof(fastnetmon_pcap_pkthdr_t)) + sizeof(fastnetmon_pcap_file_header_t)' using unsigned int (32-bit) arithmetic. With max_captured_packet_size=1500 and sizeof(fastnetmon_pcap_pkthdr_t)=16, each packet requires approximately 1516 bytes. If buffer_size_in_packets exceeds approximately 2,832,542, the multiplication overflows, resulting in a much smaller allocation than expected. Subsequent write_packet() calls then write past the allocated buffer, causing heap corruption. The buffer_size_in_packets value is derived from the ban_details_records_count configuration parameter, which is parsed using atoi() with no overflow checking.

Vendor
Pavel Odintsov
Product
Fastnetmon
CVSS
HIGH 7.1
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

Organizations running FastNetMon Community Edition for DDoS detection and network traffic analysis, particularly those with custom configurations that may set large ban_details_records_count values. System administrators responsible for network monitoring infrastructure security.

Technical summary

The allocate_buffer() function in src/packet_storage.hpp uses 32-bit unsigned integer arithmetic to calculate memory_size_in_bytes. The calculation multiplies buffer_size_in_packets by approximately 1516 bytes per packet. When buffer_size_in_packets exceeds ~2.8 million, the multiplication wraps around, causing a small buffer allocation. The write_packet() function subsequently writes beyond this undersized buffer, resulting in heap corruption. The buffer_size_in_packets value originates from the ban_details_records_count configuration parameter, parsed via atoi() without bounds checking.

Defensive priority

HIGH

Recommended defensive actions

  • Upgrade FastNetMon Community Edition to a version newer than 1.2.9 when available.
  • Review and restrict the ban_details_records_count configuration parameter to values below 2,832,542 to prevent integer overflow.
  • Validate that buffer_size_in_packets values are bounded before use in allocate_buffer().
  • Consider using 64-bit arithmetic (size_t or uint64_t) for memory size calculations to prevent overflow.
  • Monitor for unexpected process crashes or heap corruption indicators in FastNetMon deployments.
  • Apply principle of least privilege to FastNetMon processes to limit impact of potential memory corruption.

Evidence notes

CVE published 2026-05-26T17:16:53.547Z; modified 2026-05-26T21:16:42.953Z. CVSS 7.1 (HIGH). CWE-122 (Heap-based Buffer Overflow) and CWE-190 (Integer Overflow or Wraparound) identified. Vulnerability affects FastNetMon Community Edition through 1.2.9.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-48690 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-48690

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

  • CVE-2026-48690 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-48690

    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.