CVE-2026-6985

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.

CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS — Exploit Prediction

0.0015

Probability of exploitation

0.35%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-404 CWE-404

CWE-835 CWE-835

Affected Products

Vendor	Product	Versions
cesanta	mongoose	7.0 — 7.21

References

Exploits

https://github.com/dwBruijn/CVEs/blob/main/Mongoose/TCP_opt_dos.md

Other References

https://github.com/cesanta/mongoose/releases/tag/7.21 https://vuldb.com/submit/796230 https://vuldb.com/vuln/359528 https://vuldb.com/vuln/359528/cti

Frequently Asked Questions

What is CVE-2026-6985? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-6985? +

CVE-2026-6985 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0015, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-6985? +

CVE-2026-6985 affects products from cesanta, specifically: mongoose. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-6985? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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