High severity · published Apr 25, 2026
CVE-2026-6985
Cesanta Mongoose TCP Option net_builtin.c handle_opt infinite loop
7.5
CVSS
0.6%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 47% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MO
Mongoose · Cesanta
7.0; 7.1; 7.2; 7.3; 7.4; 7.5; +15 more · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-6985
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-6985
Product
https://github.com/cesanta/mongoose/releases/tag/7.21
Exploit
https://github.com/dwBruijn/CVEs/blob/main/Mongoose/TCP_opt_dos.md
Third Party Advisory
https://vuldb.com/submit/796230
Third Party Advisory
https://vuldb.com/vuln/359528
Permissions Required
https://vuldb.com/vuln/359528/cti
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