CVE-2026-73261
Received
Received - Intake
TCP/IP Stack MSS Option Handling Flaw in Mongoose
Vulnerability report for CVE-2026-73261, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-14
Last updated on: 2026-10-14
Assigner: GitHub, Inc.
Description
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.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| cesanta | mongoose | < 7.23 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-125 | The product reads data past the end, or before the beginning, of the intended buffer. |
| CWE-20 | The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. |
