{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-73261", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-08-11T17:18:01.598Z", "datePublished": "2026-10-14T18:25:41.102Z", "dateUpdated": "2026-10-14T18:25:41.102Z"}, "containers": {"cna": {"title": "Mongoose: handle_opt() missing opts[1] > len check \u2014 1-byte OOB read corrupts TCP MSS, silences mg_send() per connection", "problemTypes": [{"descriptions": [{"cweId": "CWE-20", "lang": "en", "description": "CWE-20: Improper Input Validation", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-125", "lang": "en", "description": "CWE-125: Out-of-bounds Read", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}}], "references": [{"name": "https://github.com/cesanta/mongoose/security/advisories/GHSA-3fmr-92g4-wchx", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/cesanta/mongoose/security/advisories/GHSA-3fmr-92g4-wchx"}, {"name": "https://github.com/cesanta/mongoose/commit/cc7c6d2d18c28fcc6d085633dddd88402946140a", "tags": ["x_refsource_MISC"], "url": "https://github.com/cesanta/mongoose/commit/cc7c6d2d18c28fcc6d085633dddd88402946140a"}, {"name": "https://github.com/cesanta/mongoose/releases/tag/7.23", "tags": ["x_refsource_MISC"], "url": "https://github.com/cesanta/mongoose/releases/tag/7.23"}], "affected": [{"vendor": "cesanta", "product": "mongoose", "versions": [{"version": "< 7.23", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-10-14T18:25:41.102Z"}, "descriptions": [{"lang": "en", "value": "Mongoose is an embedded web server and network library. Prior to 7.23, the built-in TCP/IP stack enabled by MG_ENABLE_TCPIP in src/net_builtin.c does not reject a TCP option whose declared opts[1] length exceeds the remaining option bytes. In handle_opt(), a NOP followed by a truncated MSS option causes opts[3] to be read outside the declared options area and used as the low byte of dmss. An unauthenticated remote peer can corrupt the per-connection MSS value so later mg_send() calls transmit truncated or zero-length application payloads while the TCP connection otherwise appears healthy. This issue is fixed in version 7.23."}], "source": {"advisory": "GHSA-3fmr-92g4-wchx", "discovery": "UNKNOWN"}}}}

{}

{"affected": [{"affectedData": [{"product": "mongoose", "vendor": "cesanta", "versions": [{"status": "affected", "version": "< 7.23"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Mongoose is an embedded web server and network library. Prior to 7.23, the built-in TCP/IP stack enabled by MG_ENABLE_TCPIP in src/net_builtin.c does not reject a TCP option whose declared opts[1] length exceeds the remaining option bytes. In handle_opt(), a NOP followed by a truncated MSS option causes opts[3] to be read outside the declared options area and used as the low byte of dmss. An unauthenticated remote peer can corrupt the per-connection MSS value so later mg_send() calls transmit truncated or zero-length application payloads while the TCP connection otherwise appears healthy. This issue is fixed in version 7.23."}], "id": "CVE-2026-73261", "lastModified": "2026-10-16T20:04:29.760", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-10-14T19:17:19.990", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/cesanta/mongoose/commit/cc7c6d2d18c28fcc6d085633dddd88402946140a"}, {"source": "security-advisories@github.com", "url": "https://github.com/cesanta/mongoose/releases/tag/7.23"}, {"source": "security-advisories@github.com", "url": "https://github.com/cesanta/mongoose/security/advisories/GHSA-3fmr-92g4-wchx"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-20"}, {"lang": "en", "value": "CWE-125"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{}