{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:bacnetstack:bacnet_stack:*:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "1.4.3"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "CPE_RANGE"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6d2d251ca4f4d932664add702b236279863d630a"
            }
          ],
          "repo": "https://github.com/bacnet-stack/bacnet-stack",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-326g-j95f-gmxv"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-758"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40279.json"
  },
  "details": "BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, decode_signed32() in src/bacnet/bacint.c reconstructs a 32-bit signed integer from four APDU bytes using signed left shifts. When any of the four bytes has bit 7 set (value ≥ 0x80), the left-shift operation overflows a signed int32_t, which is undefined behavior per the C standard. This is flagged thousands of times per minute by UndefinedBehaviorSanitizer on any BACnet input containing signed-integer property values with high-bit-set bytes. This vulnerability is fixed in 1.4.3.",
  "id": "CVE-2026-40279",
  "modified": "2026-07-08T05:38:58.024172133Z",
  "published": "2026-04-21T16:29:16.125Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40279.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-40279"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`"
}