Home/CVE/A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the
CVE

CVE-2026-6985

A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the

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.

MEDIUM · CVSS 5.3 EPSS 0.00161
Schedule remediation
  • Public exploit or PoC is available
  • SSVC automatable: yes - attacks can be scripted at scale
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-404Improper Resource Shutdown or Release
CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
▤

Affected Products & Versions

1
cesanta mongoose>= 7.0 and < 7.21
⚠

Public Exploits & PoCs

1
pocgithub.com · TCP_opt_dos.mdgithub.com
▣

Scoring & Timeline

5.3
MEDIUM · CVSS v3.1 · cna@vuldb.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD25 Apr 2026 · 05:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC triage · cisa-vulnrichment
Exploitation
poc
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
🔗

References & Sources

4
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/cesanta/mongoose/releases/tag/7.21ProductRelease Notes
https://vuldb.com/submit/796230Third Party AdvisoryVDB Entry
https://vuldb.com/vuln/359528Third Party AdvisoryVDB Entry
https://vuldb.com/vuln/359528/ctiPermissions RequiredVDB Entry
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