{"id":"CVE-2026-21870","state":"PUBLISHED","title":"The BACnet Protocol Stack library has an Off-by-one Stack-based Buffer Overflow in tokenizer_string","description":"BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. In 1.4.2, 1.5.0.rc2, and earlier, an off-by-one stack-based buffer overflow in the ubasic interpreter causes a crash (SIGABRT) when processing string literals longer than the buffer limit. The tokenizer_string function in src/bacnet/basic/program/ubasic/tokenizer.c incorrectly handles null termination for maximum-length strings. It writes a null byte to dest[40] when the buffer size is only 40 (indices 0-39), triggering a stack overflow.","publishedAt":"2026-02-13T17:58:37.205Z","updatedAt":"2026-02-13T18:19:36.183Z","severity":{"score":5.5,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["bacnet-stack bacnet-stack"],"affected":[{"vendor":"bacnet-stack","product":"bacnet-stack","versions":[{"version":"<= 1.4.2","status":"affected"},{"version":">= 1.5.0.rc1, <= 1.5.0.rc2","status":"affected"}]}],"references":["https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx","https://github.com/bacnet-stack/bacnet-stack/pull/1196","https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465"],"weaknesses":["CWE-193"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/21xxx/CVE-2026-21870.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-21870","state":"PUBLISHED","datePublished":"2026-02-13T17:58:37.205Z","dateUpdated":"2026-02-13T18:19:36.183Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-01-05T16:44:16.368Z"},"containers":{"cna":{"title":"The BACnet Protocol Stack library has an Off-by-one Stack-based Buffer Overflow in tokenizer_string","descriptions":[{"lang":"en","value":"BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. In 1.4.2, 1.5.0.rc2, and earlier, an off-by-one stack-based buffer overflow in the ubasic interpreter causes a crash (SIGABRT) when processing string literals longer than the buffer limit. The tokenizer_string function in src/bacnet/basic/program/ubasic/tokenizer.c incorrectly handles null termination for maximum-length strings. It writes a null byte to dest[40] when the buffer size is only 40 (indices 0-39), triggering a stack overflow."}],"affected":[{"vendor":"bacnet-stack","product":"bacnet-stack","versions":[{"version":"<= 1.4.2","status":"affected"},{"version":">= 1.5.0.rc1, <= 1.5.0.rc2","status":"affected"}]}],"references":[{"url":"https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx","name":"https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-pc83-wp6w-93mx","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/bacnet-stack/bacnet-stack/pull/1196","name":"https://github.com/bacnet-stack/bacnet-stack/pull/1196","tags":["x_refsource_MISC"]},{"url":"https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465","name":"https://github.com/bacnet-stack/bacnet-stack/commit/4e1176394a5ae50d2fd0b5790d9bff806dc08465","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":5.5,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-193","lang":"en","description":"CWE-193: Off-by-one Error","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-02-13T17:58:37.205Z"},"source":{"advisory":"GHSA-pc83-wp6w-93mx","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-02-13T18:19:25.750164Z","id":"CVE-2026-21870","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-02-13T18:19:36.183Z"}}]}}}