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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.

PUBLISHED Reserved 2026-04-24 | Published 2026-04-25 | Updated 2026-04-27 | Assigner VulDB




MEDIUM: 6.9CVSS: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
MEDIUM: 5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
MEDIUM: 5.3CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
5.0AV:N/AC:L/Au:N/C:N/I:N/A:P/E:POC/RL:OF/RC:C

Problem types

Infinite Loop

Denial of Service

Product status

7.0
affected

7.1
affected

7.2
affected

7.3
affected

7.4
affected

7.5
affected

7.6
affected

7.7
affected

7.8
affected

7.9
affected

7.10
affected

7.11
affected

7.12
affected

7.13
affected

7.14
affected

7.15
affected

7.16
affected

7.17
affected

7.18
affected

7.19
affected

7.20
affected

7.21
unaffected

Timeline

2026-04-24:Advisory disclosed
2026-04-24:VulDB entry created
2026-04-24:VulDB entry last update

Credits

dwbruijn (VulDB User) reporter

VulDB CNA Team coordinator

References

vuldb.com/vuln/359528 (VDB-359528 | Cesanta Mongoose TCP Option net_builtin.c handle_opt infinite loop) vdb-entry technical-description

vuldb.com/vuln/359528/cti (VDB-359528 | CTI Indicators (IOB, IOC, TTP, IOA)) signature permissions-required

vuldb.com/submit/796230 (Submit #796230 | Cesanta Mongoose 7.20 Denial of Service) third-party-advisory

github.com/dwBruijn/CVEs/blob/main/Mongoose/TCP_opt_dos.md exploit

github.com/cesanta/mongoose/releases/tag/7.21 patch

cve.org (CVE-2026-6985)

nvd.nist.gov (CVE-2026-6985)

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