FastNetMon: sFlow header_size field trusted as parser capture length causes remote out-of-bounds read

Summary

FastNetMon is a high-performance DDoS detector and sensor. In version 1.2.9 and earlier, process_sflow_flow_sample() in src/sflow_plugin/sflow_collector.cpp passes the attacker-controlled sflow_raw_protocol_header_t.header_size to parse_raw_packet_to_simple_packet_full() as its trusted captured length without comparing it with the bytes remaining in the record. An inflated header_size creates a false end pointer beyond the received sFlow v5 UDP buffer, defeating the nested parser's bounds checks and causing an unauthenticated remote out-of-bounds read and process crash, with possible limited exposure of adjacent bytes through parsed flow fields. No fixed release is available as of this review.

Remediation

1. Inventory every pavel-odintsov fastnetmon deployment, including staging.
2. No fixed version appears in the public sources yet. Check the references below and the vendor directly.

References

• Referencehttps://github.com/pavel-odintsov/fastnetmon/commit/6871b7383322db14405a8de1399a83da15ef3533
• Referencehttps://github.com/pavel-odintsov/fastnetmon/commit/be81c403b9aa891f8444a6379cd4a4fbbc324a83
• Referencehttps://github.com/pavel-odintsov/fastnetmon/pull/1089
• Referencehttps://github.com/pavel-odintsov/fastnetmon/pull/1093
• Referencehttps://github.com/pavel-odintsov/fastnetmon/security/advisories/GHSA-852r-3wcv-pjx2