{"id":"CVE-2026-48686","details":"FastNetMon Community Edition through 1.2.9 contains a stack-based buffer overflow in the BGP NLRI (Network Layer Reachability Information) decoder. The function decode_bgp_subnet_encoding_ipv4_raw() in src/bgp_protocol.cpp reads prefix_bit_length directly from the BGP packet (line 99) without validating it is \u003c= 32 for IPv4 prefixes. This value is passed to how_much_bytes_we_need_for_storing_certain_subnet_mask() which computes ceil(prefix_bit_length / 8), returning up to 32 bytes for a prefix_bit_length of 255. The result is used as the length argument to memcpy() (line 106), which copies into a 4-byte uint32_t stack variable (prefix_ipv4). This causes a stack buffer overflow of up to 28 bytes, which can be exploited for arbitrary code execution. Additionally, the unvalidated prefix_bit_length is passed to convert_cidr_to_binary_netmask_local_function_copy() (line 111), where a shift of (32 - cidr) with cidr \u003e 32 causes undefined behavior.","modified":"2026-06-18T03:56:39.143839685Z","published":"2026-05-26T00:00:00Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48686.json","cna_assigner":"mitre"},"references":[{"type":"WEB","url":"https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.cpp"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48686.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48686"},{"type":"PACKAGE","url":"https://github.com/pavel-odintsov/fastnetmon"},{"type":"ARTICLE","url":"https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48686-bgp-nlri-stack-overflow"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/pavel-odintsov/fastnetmon","events":[{"introduced":"0"},{"fixed":"394fbe06d112f9609d3d1cb10d60cbf98347c96a"}],"database_specific":{"cpe":"cpe:2.3:a:pavel-odintsov:fastnetmon:*:*:*:*:community:*:*:*","source":["DESCRIPTION","CPE_RANGE"],"extracted_events":[{"introduced":"0"},{"fixed":"1.2.9"},{"introduced":"0"},{"last_affected":"1.2.9"}]}}],"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-2026-48686.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"}]}