{"id":"CVE-2026-48689","details":"FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_object_ptr, memcpy_from_ptr, memcpy_from_object_ptr) use an incorrect bounds check of the form 'if (offset + length \u003e maximum_internal_storage_size + 1)' instead of the correct 'if (offset + length \u003e maximum_internal_storage_size)'. This allows writing exactly one byte past the end of the heap-allocated buffer. The class is used pervasively in BGP message encoding/decoding, NetFlow template processing, and Flow Spec NLRI construction. An attacker who can send network traffic (NetFlow, sFlow, IPFIX, or BGP) to a FastNetMon instance can trigger this overflow, potentially achieving arbitrary code execution by corrupting heap metadata. Notably, the append_byte() method uses the correct bounds check, confirming the inconsistency.","modified":"2026-06-18T03:55:03.206096041Z","published":"2026-05-26T00:00:00Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48689.json","cna_assigner":"mitre"},"references":[{"type":"WEB","url":"https://github.com/pavel-odintsov/fastnetmon/blob/master/src/dynamic_binary_buffer.hpp"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48689.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48689"},{"type":"PACKAGE","url":"https://github.com/pavel-odintsov/fastnetmon"},{"type":"ARTICLE","url":"https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48689-dynamic-buffer-off-by-one"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/pavel-odintsov/fastnetmon","events":[{"introduced":"0"},{"fixed":"394fbe06d112f9609d3d1cb10d60cbf98347c96a"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"1.2.9"},{"introduced":"0"},{"last_affected":"1.2.9"}],"source":["DESCRIPTION","CPE_RANGE"],"cpe":"cpe:2.3:a:pavel-odintsov:fastnetmon:*:*:*:*:community:*:*:*"}}],"versions":["v1.2.8","v1.2.7","v1.2.6","v1.2.5","v1.2.4","v1.2.3","v1.2.2","v1.2.1","v1.2.0","v1.1.9","v1.1.8","v1.1.7","v1.1.6","v1.1.5","v1.1.4","v1.1.3","v1.1.2","v1.1.0","v1.0.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-48689.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}