CVE-2026-73251

What it is

Mongoose is an embedded web server and network library. Prior to 7.23, a network attacker can impersonate a TLS server to a Mongoose client configured with a multi-certificate CA bundle. In src/tls_builtin.c, the mg_tls_init() function stores the bundle in tls->ca_bundle_der while tls->ca_der.len remains zero, and mg_tls_recv_cert() uses tls_bundle_find() to accept a Common Name match without calling mg_tls_verify_cert_signature(). A forged self-signed certificate can therefore satisfy hostname and CertificateVerify checks and enable interception, credential disclosure, traffic modification, and malicious responses. This issue is fixed in version 7.23.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-20 18:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-18 20:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 9.3 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-08-20 18:16 UTC

Last modified

2026-10-18 20:10 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-295 · Improper certificate validation

Record status

Analyzed

Affected

• Cesanta Mongoose < 7.23

Attack profile CVSS 4.0 · 9.3

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-73251.md and follow it. Check whether this project is affected by CVE-2026-73251. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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