EUVD-2026-18184
GHSA-hm7q-jq63-pr78
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Object-level authorization, IDOR prevention
|
| Impact | The CVSS score of 5.6 (Medium) with vector AV:N/AC:H/PR:N/UI:N indicates remote, unauthenticated exploitation with high attack complexity and partial impact on confidentiality, integrity, and availability. The high attack complexity (AC:H) and lack of user interaction requirement balance the network-accessible attack vector. The EPSS vector tag (E:P) confirms publicly available exploit code exists, elevating practical risk despite the medium CVSS score. KEV status is not explicitly confirmed, but public disclosure combined with POC availability signals real-world relevance. The RL:O (Official Fix) and RC:C (Confirmed) ratings indicate vendor responsiveness and stable vulnerability details. Real-world risk is elevated for systems that depend on TLS certificate validation security (embedded systems, IoT devices, firmware updaters). Organizations should prioritize patching based on deployment exposure and reliance on TLS security, not solely on CVSS score. |
| Exploit ScenarioDerived | An attacker intercepts TLS traffic to a Mongoose-based embedded device or server (e.g., IoT device, firmware update server, or embedded web interface). By exploiting the P-384 signature verification bypass, the attacker crafts a malicious certificate with an invalid signature that passes Mongoose's flawed validation logic, establishing a successful man-in-the-middle position. Publicly available exploit code simplifies execution, allowing automated attacks against vulnerable firmware versions without requiring sophisticated cryptographic knowledge. |
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Alert meAnalysisAIv1 – Apr 02, 2026
Authorization bypass in Cesanta Mongoose up to version 7.20 allows remote, unauthenticated attackers to bypass TLS certificate signature verification in the P-384 public key handler (mg_tls_verify_cert_signature function in mongoose.c), potentially enabling man-in-the-middle attacks or unauthorized access. The attack is highly complex (CVSS AC:H) but publicly disclosed exploit code exists, with vendor-released patch available in version 7.21.
RemediationAI
Vendor-released patch: Upgrade to Cesanta Mongoose version 7.21 or later, which includes the fix commit 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. This patch directly addresses the P-384 public key signature verification flaw. Installation instructions and release details are available at https://github.com/cesanta/mongoose/releases/tag/7.21. For systems unable to upgrade immediately, restrict TLS connections to trusted certificate authorities or implement certificate pinning to mitigate man-in-the-middle attack risks. No workarounds are available short of upgrade; certificate validation bypass cannot be safely mitigated at the application layer if the underlying TLS library is compromised.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
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Technical ContextAI · show details
This vulnerability affects the P-384 elliptic curve cryptography implementation within Mongoose's TLS certificate verification logic, specifically the mg_tls_verify_cert_signature function. P-384 (also known as secp384r1) is a cryptographic algorithm used in digital signature verification during TLS handshakes. The vulnerability (classified as CWE-639: Authorization Bypass Through User-Controlled Key) allows manipulation of the signature verification process, enabling attackers to forge or bypass legitimate certificate validation. This flaw directly impacts the integrity of the TLS stack in Mongoose, a lightweight embedded web server commonly used in IoT devices, firmware, and embedded systems. The CPE cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:* indicates all versions up to 7.20 are affected.
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Severity by source
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
Lifecycle Timeline
4DescriptionCVE.org
A vulnerability was determined in Cesanta Mongoose up to 7.20. Affected is the function mg_tls_verify_cert_signature of the file mongoose.c of the component P-384 Public Key Handler. Executing a manipulation can lead to authorization bypass. The attack can be executed remotely. Attacks of this nature are highly complex. The exploitability is told to be difficult. The exploit has been publicly disclosed and may be utilized. Upgrading to version 7.21 is able to address this issue. This patch is called 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. The affected component should be upgraded. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
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The mg_tls_init function in Cesanta Mongoose HTTPS server 7.0 and 6.7-6.18 (compiled with mbedTLS support) is vulnerable
The mg_http_serve_file function in Cesanta Mongoose HTTP server 7.0 is vulnerable to remote OOB write attack via connect
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