{"id":"CVE-2026-71263","state":"PUBLISHED","title":"FreeModbus LINUXTCP Port Off-by-One Global Buffer Overflow in xMBPortTCPPool()","description":"The LINUXTCP port of FreeModbus contains an off-by-one bounds check in xMBPortTCPPool (demo/LINUXTCP/port/porttcp.c). The check uses a strict greater-than comparison instead of greater-than-or-equal against the 263-byte MB_TCP_BUF_SIZE limit.","publishedAt":"2026-08-05T12:26:11.423Z","updatedAt":"2026-08-10T11:46:28.356Z","severity":{"score":9.1,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","source":"TuranSec"},"assigner":"TuranSec","products":["cwalter-at FreeModbus"],"affected":[{"vendor":"cwalter-at","product":"FreeModbus","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"*","versionType":"custom"}],"programFiles":["demo/LINUXTCP/port/porttcp.c"]}],"references":["https://github.com/cwalter-at/freemodbus","https://github.com/cwalter-at/freemodbus/blob/master/demo/LINUXTCP/port/porttcp.c"],"weaknesses":["CWE-787"],"ingestedAt":"2026-10-29T20:12:49.727Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/71xxx/CVE-2026-71263.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-71263","state":"PUBLISHED","datePublished":"2026-08-05T12:26:11.423Z","dateUpdated":"2026-08-10T11:46:28.356Z","assignerShortName":"TuranSec","assignerOrgId":"309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c","dateReserved":"2026-08-05T12:23:34.966Z"},"containers":{"cna":{"title":"FreeModbus LINUXTCP Port Off-by-One Global Buffer Overflow in xMBPortTCPPool()","descriptions":[{"lang":"en","value":"The LINUXTCP port of FreeModbus contains an off-by-one bounds check in xMBPortTCPPool (demo/LINUXTCP/port/porttcp.c). The check uses a strict greater-than comparison instead of greater-than-or-equal against the 263-byte MB_TCP_BUF_SIZE limit."}],"affected":[{"vendor":"cwalter-at","product":"FreeModbus","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"*","versionType":"custom"}],"programFiles":["demo/LINUXTCP/port/porttcp.c"]}],"references":[{"url":"https://github.com/cwalter-at/freemodbus","tags":["third-party-advisory"]},{"url":"https://github.com/cwalter-at/freemodbus/blob/master/demo/LINUXTCP/port/porttcp.c","tags":["third-party-advisory"]}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","baseScore":9.1,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"HIGH"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-787","lang":"en","description":"CWE-787","type":"CWE"}]}],"providerMetadata":{"shortName":"TuranSec","orgId":"309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c","dateUpdated":"2026-08-10T11:46:28.356Z"},"credits":[{"lang":"en","value":"Alibek Baxtiyorov","type":"finder"}],"source":{"discovery":"EXTERNAL"},"datePublic":"2026-08-05T12:26:11.423Z"},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-05T15:39:27.280961Z","id":"CVE-2026-71263","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-05T15:39:36.370Z"}}]}}}