{"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":"2026-04-21T19:18:58.492Z"},"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 ≥ 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"}},"adp":[{"references":[{"url":"https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-04-21T19:18:55.401000Z","id":"CVE-2026-40279","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-04-21T19:18:58.492Z"}}]}}