CVE-2025-15387

High

Published: 31 December 2025

Published

31 December 2025

Modified

15 April 2026

KEV Added

—

Patch

—

CVSS Score 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Score 0.0014 33.7th percentile

Risk Priority 18 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2025-15387 is a high-severity Insufficient Entropy (CWE-331) vulnerability in Org (inferred from references). Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 33.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 IA-5 (Authenticator Management) and SC-23 (Session Authenticity).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 2 other techniques. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

IA-5 Authenticator Management good match

prevent

IA-5 requires authenticators, including session tokens, to have sufficient strength of mechanism such as adequate entropy to resist brute-force attacks.

SC-23 Session Authenticity good match

prevent

SC-23 protects the authenticity of communications sessions against hijacking via brute-force guessing of session identifiers.

AC-7 Unsuccessful Logon Attempts partial match

prevent

AC-7 limits consecutive unsuccessful attempts, mitigating brute-force attacks on session tokens even if entropy is insufficient.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1110 Brute Force Credential Access

Adversaries may use brute force techniques to gain access to accounts when passwords are unknown or when password hashes are obtained.

attack.mitre.org →

T1606.001 Web Cookies Credential Access

Adversaries may forge web cookies that can be used to gain access to web applications or Internet services.

attack.mitre.org →

Why these techniques?

Vulnerability in public-facing VPN Firewall enables unauthenticated remote brute-force (T1110) and forging (T1606.001) of predictable session tokens via exploitation (T1190).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

VPN Firewall developed by QNO Technology has a Insufficient Entropy vulnerability, allowing unauthenticated remote attackers to obtain any logged-in user session through brute-force attacks and subsequently log into the system.

Deeper analysisAI

CVE-2025-15387 is an Insufficient Entropy vulnerability (CWE-331) affecting the VPN Firewall developed by QNO Technology. Published on 2025-12-31, this flaw stems from inadequate randomness in session handling, enabling unauthenticated remote attackers to brute-force and obtain session tokens of any logged-in user, thereby allowing them to log into the system. The vulnerability carries a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H), indicating high severity with network accessibility, low complexity, no privileges required, user interaction needed, and substantial impacts on confidentiality, integrity, and availability.

Unauthenticated remote attackers can exploit this vulnerability by launching brute-force attacks against session identifiers exposed over the network. Success grants attackers full access to the system under the context of the targeted logged-in user, potentially compromising sensitive data, modifying configurations, or disrupting services.

Advisories from TWCERT/CC detail mitigation strategies and are available at https://www.twcert.org.tw/en/cp-139-10614-dee41-2.html and https://www.twcert.org.tw/tw/cp-132-10613-e1780-1.html.