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Vulnerability · Published Apr 25, 2026 · Assigned by VulDB

CVE-2026-6985Cesanta Mongoose TCP Option net_builtin.c handle_opt infinite loop

Medium 5.3

In plain English

A medium-severity infinite loop in Mongoose from Cesanta. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.6%top 52.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12swupdateno fix listedDEBIAN-CVE-2026-6985
Debian:13swupdateno fix listedDEBIAN-CVE-2026-6985
Debian:14swupdate2025.12+dfsg-10DEBIAN-CVE-2026-6985
Ubuntu:22.04:LTSswupdateno fix listedUBUNTU-CVE-2026-6985
Ubuntu:24.04:LTSswupdateno fix listedUBUNTU-CVE-2026-6985
Ubuntu:25.10swupdateno fix listedUBUNTU-CVE-2026-6985
Ubuntu:26.04:LTSswupdateno fix listedUBUNTU-CVE-2026-6985
Ubuntu:26.10swupdateno fix listedUBUNTU-CVE-2026-6985

Affected products (as reported)

VendorProductVersions
Cesanta Mongoose 7.07.17.27.37.47.57.67.7

Weakness: CWE-835, CWE-404 · Vector: 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

References