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TI-2026-06113 Aliases CVE-2026-6985GHSA-3ppf-435x-3p66

Cesanta Mongoose TCP Option net_builtin.c handle_opt infinite loop

Priority HIGH 70CWE-404Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-404.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00565 47th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by the CNA and NVD
Fix Fixed Mongoose (Cesanta): 7.21

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
CesantaMongoose7.0; 7.1; 7.2; 7.3; 7.4; 7.5; 7.6; 7.7; 7.8; 7.9; 7.10; 7.11; 7.12; 7.13; 7.14; 7.15; 7.16; 7.17; 7.18; 7.19; 7.207.21Patch availableCNA
  • Mongoose VendorCesanta Affected 7.0; 7.1; 7.2; 7.3; 7.4; 7.5; 7.6; 7.7; 7.8; 7.9; 7.10; 7.11; 7.12; 7.13; 7.14; 7.15; 7.16; 7.17; 7.18; 7.19; 7.20 Fixed in 7.21 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:*7.0 to before 7.21VulnerableCesanta
  • cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:* Versions 7.0 to before 7.21 Vulnerable ·Cesanta

Remediation

  • Fix · CNA Mongoose (Cesanta) Fixed in 7.21

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-6985
  2. 2026-10-03 Alias added: GHSA-3ppf-435x-3p66
  3. 2026-10-25 EPSS moved to the below the 50th percentile

References

Exploit 1

Patch 1

  • TI-2026-51393 Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling CVSS 3.1CRITICAL 9.1
  • TI-2026-51389 Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching CVSS 4.0CRITICAL 9.1
  • TI-2023-02723 Cesanta Mongoose MQTT Message Parsing Heap Overflow CVSS 3.1HIGH 8.8
  • TI-2020-15865 Buffer overflow in mg_resolve_from_hosts_file in Mongoose 6.18, when reading from a crafted hosts file. CVSS 3.1HIGH 8.8
  • TI-2023-17032 The HTTP server in Mongoose before 7.10 accepts requests containing negative… CVSS 3.1HIGH 7.5
  • TI-2019-13923 An integer overflow in parse_mqtt in mongoose.c in Cesanta Mongoose 6.16 allows an… CVSS 3.1CRITICAL 9.8
See all 54 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences