{"id":"CVE-2026-40279","state":"PUBLISHED","title":"BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`","description":"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.","publishedAt":"2026-04-21T16:29:16.125Z","updatedAt":"2026-04-21T19:18:58.492Z","severity":{"score":3.7,"label":"Low","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["bacnet-stack bacnet-stack"],"affected":[{"vendor":"bacnet-stack","product":"bacnet-stack","versions":[{"version":"< 1.4.3","status":"affected"}]}],"references":["https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv"],"weaknesses":["CWE-758"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/40xxx/CVE-2026-40279.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-40279","state":"PUBLISHED","datePublished":"2026-04-21T16:29:16.125Z","dateUpdated":"2026-04-21T19:18:58.492Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-04-10T20:22:44.034Z"},"containers":{"cna":{"title":"BACnet Stack: Undefined-behavior signed left shift in `decode_signed32()`","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."}],"affected":[{"vendor":"bacnet-stack","product":"bacnet-stack","versions":[{"version":"< 1.4.3","status":"affected"}]}],"references":[{"url":"https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv","name":"https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-326g-j95f-gmxv","tags":["x_refsource_CONFIRM"]}],"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-758","lang":"en","description":"CWE-758: Reliance on Undefined, Unspecified, or Implementation-Defined Behavior","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-04-21T16:29:16.125Z"},"source":{"advisory":"GHSA-326g-j95f-gmxv","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","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"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-21T19:18:58.492Z"}}]}}}