CVE-2026-73261Network attack vectorHinoki check available

Data-flow denial via unchecked TCP option length

Published Oct 14, 2026 · Updated Oct 14, 2026

TCP-option parsing in Cesanta Mongoose before 7.23 allows remote attackers to block application data via malformed TCP options. The handle_opt() function in src/net_builtin.c trusts an option length exceeding the remaining bytes, reading beyond the option area into the connection's MSS value. With MG_ENABLE_TCPIP=1, inbound or outbound TCP connections transmit truncated or zero-length application payloads while remaining open.

CVSS severity7.5
High
EPSS probability0.35%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
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Summary

What happened

TCP-option parsing in Cesanta Mongoose before 7.23 allows remote attackers to block application data via malformed TCP options. The handle_opt() function in src/net_builtin.c trusts an option length exceeding the remaining bytes, reading beyond the option area into the connection's MSS value. With MG_ENABLE_TCPIP=1, inbound or outbound TCP connections transmit truncated or zero-length application payloads while remaining open.

The record

CVE
CVE-2026-73261
Published
Oct 14, 2026
Updated
Oct 14, 2026
Vendor
Cesanta
Product
Mongoose
Classifications
CWE-125, CWE-20, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 7.23

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cesanta · Mongooseversion=< 7.23

Published CVSS scores

7.5GitHub_MCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
CWE-20Improper Input Validation
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

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Your stack

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