Security advisory

{
  "id": "a0098f730abf38cd57854fc97962590662e18cd995bb6e44789ac694432e927f",
  "url": "https://osv.dev/vulnerability/CVE-2026-48686",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2026-48686",
    "summary": "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 <= 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 > 32 causes undefined behavior.",
    "evidence": "osv:CVE-2026-48686",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-48686",
      "aliases": [
        "CVE-2026-48686"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/pavel-odintsov/fastnetmon",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "last_affected": "394fbe06d112f9609d3d1cb10d60cbf98347c96a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "1.2.9"
                      }
                    ],
                    "source": "DESCRIPTION"
                  },
                  {
                    "cpe": "cpe:2.3:a:pavel-odintsov:fastnetmon:*:*:*:*:community:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "1.2.9"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.2.9",
            "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/cve-osv-conversion/osv-output/CVE-2026-48686.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:28.956376036Z",
      "provider": "osv",
      "references": [
        "https://github.com/pavel-odintsov/fastnetmon/blob/master/src/bgp_protocol.cpp",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48686.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-48686",
        "https://github.com/pavel-odintsov/fastnetmon",
        "https://lorikeetsecurity.com/blog/fastnetmon-cve-2026-48686-bgp-nlri-stack-overflow"
      ],
      "provider_metadata": {
        "cna_assigner": "mitre",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "last_affected": "32"
                  },
                  {
                    "last_affected": "28"
                  }
                ],
                "source": "DESCRIPTION"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48686.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-48686",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 495746,
  "published_at": "2026-05-26T00:00:00+00:00"
}