CVE-2026-6985

Cesanta Mongoose TCP Option net_builtin.c handle_opt infinite loop

State: Published
Severity: 6.9 Medium
Published: Apr 25, 2026
Updated: Apr 27, 2026
Reserved: Apr 24, 2026

Description

A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the file /src/net_builtin.c of the component TCP Option Handler. This manipulation of the argument optlen causes infinite loop. The attack is possible to be carried out remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 7.21 is able to resolve this issue. Upgrading the affected component is advised. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Scores

CVSS	Score	Vector	Source
4.0	6.9 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P	VulDB
3.1	5.3 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C	VulDB
3.0	5.3 Medium	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C	VulDB
2.0	5.0 Medium	AV:N/AC:L/Au:N/C:N/I:N/A:P/E:POC/RL:OF/RC:C	VulDB

Weaknesses

CWE-835 Infinite Loop
CWE-404 Denial of Service

Affected Products

Product	Versions
MongooseCesanta	7.0Affected 7.1Affected 7.2Affected 7.3Affected 7.4Affected 7.5Affected 7.6Affected 7.7Affected 7.8Affected 7.9Affected 7.10Affected 7.11Affected 7.12Affected 7.13Affected 7.14Affected 7.15Affected 7.16Affected 7.17Affected 7.18Affected 7.19Affected 7.20Affected 7.21Not affected

References

VDB-359528 | Cesanta Mongoose TCP Option net_builtin.c handle_opt infinite loopvdb-entrytechnical-description
VDB-359528 | CTI Indicators (IOB, IOC, TTP, IOA)signaturepermissions-required
Submit #796230 | Cesanta Mongoose 7.20 Denial of Servicethird-party-advisory
https://github.com/dwBruijn/CVEs/blob/main/Mongoose/TCP_opt_dos.mdexploit
https://github.com/cesanta/mongoose/releases/tag/7.21patch

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