CVE-2026-73261
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.
- Score
- CVSS 3.1 7.5 High
- Status
- Deferred - security-advisories@github.com
- Published
- 2026-10-14
- Last modified
- 2026-10-16
- Weaknesses
- CWE-125, CWE-20
Affected products
References
- https://github.com/cesanta/mongoose/security/advisories/GHSA-3fmr-92g4-wchx
- https://github.com/cesanta/mongoose/commit/cc7c6d2d18c28fcc6d085633dddd88402946140a
- https://github.com/cesanta/mongoose/releases/tag/7.23
