{"id":"CVE-2026-73261","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-73261","generatedAt":"2026-10-28T02:55:31.848Z","title":"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.","description":"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.","published":"2026-10-14T19:17:20.000Z","lastModified":"2026-10-16T20:04:30.000Z","status":"Deferred","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-20","CWE-125"],"affected":[],"epss":{"score":0.00349,"percentile":0.28344,"date":"2026-10-26","history":[{"date":"2026-10-15","score":0.00349,"percentile":0.26933}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.35%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-14T19:17:20.000Z","detail":{"score":"7.5","severity":"HIGH","publishedAt":"2026-10-14T19:17:19.990Z"},"summary":"New CVE, high severity (CVSS 7.5)."}],"references":[{"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","source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-73261","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}