{"id":"CVE-2026-93424","kind":"vulnerability","aliases":["CVE-2026-93424"],"related":[],"title":"FastNetMon: NetFlow template race lets remote senders crash the detector","description":"FastNetMon is a high-performance DDoS detector and sensor. In version 1.2.9 and earlier, peer_find_template() in src/netflow_plugin/netflow_collector.cpp and src/netflow_plugin/netflow_v9_collector.cpp returns a pointer into global_netflow9_templates after releasing the cache mutex. On deployments with at least two entries in netflow_ports, concurrent template redefinition and data-flowset processing can let add_update_peer_template() reassign the template and free its records vector while another listener dereferences the escaped pointer. An unauthenticated sender that can reach both NetFlow/IPFIX listener ports can trigger a heap-use-after-free and reliably crash FastNetMon. No fixed release is available as of this review.","summary":"FastNetMon, a DDoS detector, has a race in its NetFlow template cache where a pointer is used after the memory it points to has been freed. An unauthenticated sender that can reach two NetFlow/IPFIX listener ports can trigger a heap use-after-free and reliably crash the process.","severity":"high","cvss":7.5,"epss":null,"exploited":false,"exploited_at":null,"products":[{"name":"fastnetmon","fixed":[],"affected":"<= 1.2.9","ecosystem":"vendor"}],"ecosystems":[],"tags":["ddos-detection","fastnetmon","ipfix","netflow","package","self-hosted"],"not_affected_if":["single-netflow-port","trusted-exporters-only","version-above-1.2.9"],"how_to_check":"- Check the FastNetMon config (/etc/fastnetmon.conf) for `netflow_port`: the advisory's PoC precondition is two or more ports, e.g. `netflow_port = 2055,2056`. A single port was the negative control and did not crash.\n- Check the version: `fastnetmon --version`; 1.2.9 and earlier are listed affected, and no released version is listed as patched. A source build is fixed only if it includes commit a24e528.\n- Check whether those UDP ports are reachable from networks other than your trusted exporters.","fix":"No patched release: the advisory lists patched versions as None (affected <= 1.2.9). Commit a24e528 (2026-07-20) 'Moved to logic to new copy of template to address security issue GHSA-ph88-95vc-x6gv' changes ipfix_collector.cpp and netflow_v9_collector.cpp; build from a source revision that includes it. Until then, run a single NetFlow/IPFIX listener port and restrict UDP access to trusted exporters.","status":"open","published_at":"2026-11-05T23:17:02+00:00","first_seen_at":"2026-11-05T23:48:40+00:00","triaged_at":"2026-11-05T23:49:41+00:00","updated_at":"2026-11-05T23:50:30+00:00","category":"package","confidence":0.85,"triage":{"at":"2026-11-05T23:49:41Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"FastNetMon: NetFlow template race lets remote senders crash the detector","impact":"low","summary":"FastNetMon, a DDoS detector, has a race in its NetFlow template cache where a pointer is used after the memory it points to has been freed. An unauthenticated sender that can reach two NetFlow/IPFIX listener ports can trigger a heap use-after-free and reliably crash the process.","audience":"businesses","category":"package","nicknames":[],"who_cares":["fastnetmon","netflow","ipfix","self-hosted","ddos-detection"],"confidence":0.7,"fix_status":"none","needs_auth":"no","worst_case":"FastNetMon process crashes repeatedly from unauthenticated network packets","analyst_note":"Sources list a Patch and a Vendor advisory on github.com but the text states no fixed release exists; confirm current fix status and affected version range from the vendor advisory.","how_to_check":"- Check whether `netflow_ports` in the FastNetMon configuration lists at least two entries.\n- Check the installed version; versions `1.2.9` and earlier are affected.\n- Check whether the NetFlow/IPFIX listener ports are reachable from untrusted networks.","plain_action":"","needs_analyst":true,"not_affected_if":["single-netflow-port","trusted-exporters-only","version-above-1.2.9"],"who_is_affected":"Deployments of FastNetMon `1.2.9` and earlier that have at least two entries in `netflow_ports` and accept NetFlow or IPFIX traffic from senders that can reach both listener ports. Installations with a single NetFlow port, or with those ports reachable only from trusted exporters, are less exposed. The sources state that no fixed release is available as of this review.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000766,"input_tokens":4393,"output_tokens":653,"severity_before":"high"},"analyst_status":"done","analyst_note":"Sources list a Patch and a Vendor advisory on github.com but the text states no fixed release exists; confirm current fix status and affected version range from the vendor advisory.","search":"'-2026':12A,15A '-93424':13A,16A '1.2.9':89C 'add':131C 'anoth':144C 'avail':176C 'cach':39B,109C 'concurr':121C 'crash':8A,74B,170C 'cve':11A,14A 'data':126C 'data-flowset':125C 'ddos':19B,30B,83C 'ddos-detect':18B 'deploy':112C 'derefer':146C 'detect':20B 'detector':10A,31B,84C 'earlier':91C 'entri':117C 'escap':148C 'fastnetmon':1A,17A,21B,28B,77C,171C 'find':93C 'fix':173C 'flowset':127C 'free':71B,139C,167C 'freed':53B 'global':103C 'heap':67B,164C 'heap-use-after-fre':163C 'high':81C 'high-perform':80C 'host':27B 'ipfix':22B 'least':115C 'let':5A,130C 'listen':62B,145C,158C 'memori':47B 'mutex':110C 'netflow':2A,23B,37B,119C 'netflow/ipfix':61B,157C 'netflow9':104C 'packag':24B 'peer':92C,133C 'perform':82C 'point':49B 'pointer':42B,101C,149C 'port':63B,120C,159C 'process':76B,128C 'race':4A,34B 'reach':59B,155C 'reassign':135C 'record':141C 'redefinit':123C 'releas':107C,174C 'reliabl':73B,169C 'remot':6A 'return':99C 'review':180C 'self':26B 'self-host':25B 'sender':7A,56B,152C 'sensor':86C 'src/netflow_plugin/netflow_collector.cpp':96C 'src/netflow_plugin/netflow_v9_collector.cpp':98C 'templat':3A,38B,94C,105C,122C,134C,137C 'trigger':65B,161C 'two':60B,116C 'unauthent':55B,151C 'updat':132C 'use':44B,69B,165C 'use-after-fre':68B 'vector':142C 'version':88C","nicknames":[],"mitigations":[],"who_affected":"FastNetMon 1.2.9 and earlier with two or more NetFlow v9/IPFIX listener ports configured. Any host that can send UDP to two of those ports can crash the daemon within seconds, leaving the monitored network without DDoS detection. Single-port setups, or ports reachable only from trusted exporters, can skip it. The advisory says escalation beyond a crash is plausible but was not attempted.","tier":"B","verified":{"fix":{"at":"2026-11-05T23:50:30Z","by":"analyst","doc":"https://github.com/pavel-odintsov/fastnetmon/commit/a24e528d145b5371a7ab0bcdde23e4b4b99506e9","run_id":1840},"products":{"at":"2026-11-05T23:50:30Z","by":"analyst","doc":"https://github.com/pavel-odintsov/fastnetmon/commit/a24e528d145b5371a7ab0bcdde23e4b4b99506e9","run_id":1840},"how_to_check":{"at":"2026-11-05T23:50:30Z","by":"analyst","doc":"https://github.com/pavel-odintsov/fastnetmon/commit/a24e528d145b5371a7ab0bcdde23e4b4b99506e9","run_id":1840},"who_affected":{"at":"2026-11-05T23:50:30Z","by":"analyst","doc":"https://github.com/pavel-odintsov/fastnetmon/commit/a24e528d145b5371a7ab0bcdde23e4b4b99506e9","run_id":1840}},"analyst_revisit_at":null,"fix_status":"none","audience":"businesses","plain_action":null,"pkeys":["fastnetmon"],"ptokens":["fastnetmon"],"labels":["ddosdetection","fastnetmon","high","ipfix","netflow","package","selfhosted"],"campaign_type":null,"first_public_at":"2026-07-20T14:30:23+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cvss_by":"security-advisories@github.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-93424","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93424","severity":null,"published_at":"2026-11-05T23:17:02+00:00","modified_at":"2026-11-05T23:17:02+00:00","first_seen_at":"2026-11-05T23:48:40+00:00","fetched_at":"2026-11-05T23:48:40+00:00","note":null},{"source":"analyst","external_id":"CVE-2026-93424:1840","url":null,"severity":null,"published_at":"2026-11-05T23:50:30+00:00","modified_at":"2026-11-05T23:50:30+00:00","first_seen_at":"2026-11-05T23:50:30+00:00","fetched_at":"2026-11-05T23:50:30+00:00","note":"Read GHSA-ph88-95vc-x6gv and commit a24e528: patched versions None, fix commit on source only. Corrected config key to netflow_port per PoC. PoC is in the advisory (not separately linked); no exploitation reported."}],"documents":[{"id":81514,"url":"https://github.com/pavel-odintsov/fastnetmon/commit/a24e528d145b5371a7ab0bcdde23e4b4b99506e9","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":81515,"url":"https://github.com/pavel-odintsov/fastnetmon/security/advisories/GHSA-ph88-95vc-x6gv","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-07-20T14:30:23+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"}],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}