{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-40279", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-04-10T20:22:44.034Z", "datePublished": "2026-04-21T16:29:16.125Z", "dateUpdated": "2026-04-21T16:29:16.125Z"}, "containers": {"cna": {"title": "BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`", "problemTypes": [{"descriptions": [{"cweId": "CWE-758", "lang": "en", "description": "CWE-758: Reliance on Undefined, Unspecified, or Implementation-Defined Behavior", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 3.7, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}}], "references": [{"name": "https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv"}], "affected": [{"vendor": "bacnet-stack", "product": "bacnet-stack", "versions": [{"version": "< 1.4.3", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-04-21T16:29:16.125Z"}, "descriptions": [{"lang": "en", "value": "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 \u2265 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."}], "source": {"advisory": "GHSA-326g-j95f-gmxv", "discovery": "UNKNOWN"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "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 \u2265 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", "lastModified": "2026-04-21T17:16:54.853", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 3.7, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 1.4, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-04-21T17:16:54.853", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-758"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,1.4.3)"}}], "enrichment": {"confidence": 98.0, "confidence_source": "matching", "scores": [{"score": 98.0, "source": "matching"}]}, "original": {"product": "bacnet-stack", "source": "cna", "vendor": "bacnet-stack"}, "product": "bacnet_stack", "vendor": "bacnetstack"}], "created": "2026-04-21T17:30:37.393501+00:00", "updated": "2026-04-21T17:30:37.393600+00:00", "vendors": ["bacnetstack", "bacnetstack$PRODUCT$bacnet_stack"]}