CVE-2026-92698
FastNetMon: sFlow header_size field trusted as parser capture length causes remote out-of-bounds read
What happened?
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.
Affected software and versions
| Software | Version information | Fixed version |
|---|---|---|
| fastnetmonpavel-odintsov | affected: <= 1.2.9 | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.
Sources and remediation references
- https://www.cve.org/CVERecord?id=CVE-2026-92698
- https://github.com/pavel-odintsov/fastnetmon/security/advisories/GHSA-852r-3wcv-pjx2
- https://github.com/pavel-odintsov/fastnetmon/pull/1089
- https://github.com/pavel-odintsov/fastnetmon/pull/1093
- https://github.com/pavel-odintsov/fastnetmon/commit/6871b7383322db14405a8de1399a83da15ef3533
- https://github.com/pavel-odintsov/fastnetmon/commit/be81c403b9aa891f8444a6379cd4a4fbbc324a83