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No exploitation reportedFix available

CVE-2026-11404

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

No exploitation reported by the sources we read.

  • Published2026-07-09
  • WeaknessCWE-125

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2026-07-0915:13CVE publishedCNA

Versions per branch

Products declared by the CNA1 product

As VulnCheck, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • Cesanta Mongooseother versions: not affected
    Affected
    • < 7.22fixed in 7.22custom

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-08-29

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • Mongoose_jllJuliaall versions · no fixed version listed
  • mongooseUbuntu:26.10all versions · no fixed version listed
  • mongooseDebian:14all versions · fixed in 7.22+ds-1

Full record on NVD

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 4.0 vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Published
2026-07-09
Last Modified
2026-11-03
NVD status
Deferred
GitHub Advisory
GHSA-cvgj-gr8r-q762

Frequently asked questions

What is CVE-2026-11404?

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.

Is CVE-2026-11404 actively exploited?

Active exploitation of CVE-2026-11404 has not been confirmed. Its EPSS score was 0.8% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-11404?

CVE-2026-11404 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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