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CVE-2026-73261GHSA-3fmr-92g4-wchx

Mongoose: handle_opt() missing opts[1] > len check — 1-byte OOB read corrupts TCP MSS, silences mg_send() per connection

cesanta mongoose
Open in ThreatlineRecord JSON
CVSS
7.5High
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.35%Chance of exploitation activity in the next 30 days, higher than 27% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published14 Oct 2026Updated 14 Oct 2026CVE List

What fixes it

No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.

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.

Text from CVE List

Affected versions 1

  • mongooseaffected: < 7.23CVE List

References 3