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TI-2026-09841 Aliases CVE-2026-11404GHSA-cvgj-gr8r-q762

Cesanta Mongoose Out-of-Bounds Read in MG_TLS_BUILTIN ClientHello Session ID Parsing

Priority MEDIUM 45CWE-125Published · 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 · High
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-125 and the CVSS impact.

Summary

Cesanta Mongoose before 7.22 contains an out-of-bounds read in the built-in TLS server function mg_tls_server_recv_hello(), which uses an attacker-controlled session_id_len byte from a TLS ClientHello as a buffer index without validating it against the length of received data. A remote, unauthenticated attacker can send a single crafted ClientHello with an oversized session id length to read past the receive buffer, crashing any HTTPS, MQTTS, or WSS service built on MG_TLS_BUILTIN.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00784 56th percentileScored 2026-11-07
Fix Fixed Mongoose (Cesanta): 7.22

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
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
CesantaMongoosebefore 7.227.22Patch availableCNA
  • Mongoose VendorCesanta Affected before 7.22 Fixed in 7.22 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:*——Cesanta
  • cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:* Versions — — ·Cesanta

Remediation

  • Fix · CNA Mongoose (Cesanta) Fixed in 7.22

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-11404
  2. 2026-10-03 Alias added: GHSA-cvgj-gr8r-q762
  3. 2026-11-04 EPSS moved to the 50th–90th percentile

References

Patch 1

Other 1

  • TI-2023-23198 Cesanta mjs v2.20.0 was discovered to contain a function pointer hijacking vulnerability… CVSS 3.1CRITICAL 9.8
  • TI-2026-51393 Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling CVSS 3.1CRITICAL 9.1
  • TI-2018-15418 Mongoose Web Server 6.9 Denial of Service via Socket Connection CVSS 4.0HIGH 8.7
  • 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
See all 154 →

Sources

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