{"id":"UBUNTU-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":"2026-06-16T05:00:07.069967749Z","published":"2026-05-26T16:16:00Z","related":["USN-8429-1"],"upstream":["CVE-2026-48686"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-48686"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-48686"},{"type":"REPORT","url":"https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48686-bgp-nlri-stack-overflow"},{"type":"REPORT","url":"https://github.com/pavel-odintsov/fastnetmon/pull/1053"},{"type":"REPORT","url":"https://github.com/pavel-odintsov/fastnetmon/commit/265a767635767d7a08391dbe7f98f750d2ea04d0"},{"type":"REPORT","url":"https://github.com/pavel-odintsov/fastnetmon"},{"type":"REPORT","url":"https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.cpp"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8429-1"}],"affected":[{"package":{"name":"fastnetmon","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/fastnetmon?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2.6-1ubuntu0.1~esm1"}]}],"versions":["1.2.5-1","1.2.6-1","1.2.6-1build1","1.2.6-1build2","1.2.6-1build3","1.2.6-1build4"],"ecosystem_specific":{"binaries":[{"binary_name":"fastnetmon","binary_version":"1.2.6-1ubuntu0.1~esm1"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48686.json"}},{"package":{"name":"fastnetmon","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/fastnetmon?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.2.8-1build1","1.2.8-1build2","1.2.8+git20250911-1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.2.8+git20250911-1","binary_name":"fastnetmon"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-48686.json"}},{"package":{"name":"fastnetmon","ecosystem":"Ubuntu:Pro:26.04:LTS","purl":"pkg:deb/ubuntu/fastnetmon?arch=source&distro=esm-apps%2Fresolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2.8+git20250911-2ubuntu0.1~esm1"}]}],"versions":["1.2.8+git20250911-1","1.2.8+git20250911-1build1","1.2.8+git20250911-1build2","1.2.8+git20250911-2"],"ecosystem_specific":{"binaries":[{"binary_name":"fastnetmon","binary_version":"1.2.8+git20250911-2ubuntu0.1~esm1"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-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"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}