Out-of-bounds Read in Cesanta Mongoose
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (47.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 47.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Cesanta Mongoose — versions 0
Weakness classification (CWE)
References
- github.com/cesanta/mongoose/releases/tag/7.22 (release-notes, patch)
- github.com/cesanta/mongoose (product)
- Patch Commit (patch)
- www.vulncheck.com/advisories/cesanta-mongoose-out-of-bounds-read-in-mg-tls-buil… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-11404?
- CVE-2026-11404 is a high-severity vulnerability in Cesanta Mongoose, classified under Out-of-bounds Read. CVSS score: 7.5/10. Published 2026-07-09.
- How severe is CVE-2026-11404?
- High severity. CVSS v3 base score is 7.5 out of 10.