← Vulnerability feed

Vulnerability record · CVE-2026-73251 · published 20 August 2026

CVE-2026-73251: Improper certificate validation vulnerability

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.

9.3 CVSS 4.0 Critical EPSS 0.33% · top 76.8% CWE-295 · Improper certificate validation Awaiting Analysis
9.3CVSS 4.0 base score
0.33%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
6References
9 Sep 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/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:

References

LinkTags
https://github.com/cesanta/mongoose/commit/2988bc9df3a5efc9539471cb7455975fa25df483
https://github.com/cesanta/mongoose/releases/tag/7.23
https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8
https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8
https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8
https://github.com/cesanta/mongoose/security/advisories/GHSA-qj6j-2692-v2r8

Track CVE-2026-73251 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2026-85102Checkpoint gaia embedded improper certificate validation vulnerabilityImproper certificate trust validation during VPN negotiation in Check Point Quantum Security Gateway may allow an unauthenticated remote attacker to …KEVEPSS 0.99%5.5CVE-2023-41991Apple iOS, iPadOS and macOS certificate validation bypassApple iOS, iPadOS and macOS contain an improper certificate validation flaw (CWE-295) that lets a malicious app bypass signature validation. Apple st…KEVEPSS 13%analysed7.8CVE-2023-20963Android WorkSource parcel mismatch local privilege escalationCVE-2023-20963 is a parcel mismatch in Android's WorkSource component that allows a local attacker to escalate privileges without additional executio…KEVEPSS 1.5%analysed8.8CVE-2022-26923Microsoft Active Directory Domain Services certificate validation privilege escalationActive Directory Domain Services fails to properly validate certificate attributes, allowing a low-privileged domain user to obtain a certificate tha…KEVEPSS 84%analysed8.0CVE-2022-20703Cisco Small Business RV Series Routers stack-based buffer overflowCVE-2022-20703 covers multiple vulnerabilities in Cisco Small Business RV160, RV260, RV340 and RV345 Series Routers, including a stack-based buffer o…KEVEPSS 9.2%analysed8.1CVE-2020-0601Windows CryptoAPI ECC certificate validation spoofing flawWindows CryptoAPI (Crypt32.dll) improperly validates Elliptic Curve Cryptography certificates, allowing a spoofed code-signing certificate to be trus…KEVEPSS 89%analysed

Source: NIST National Vulnerability Database (record CVE-2026-73251), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.