What is the CVSS score of CVE-2026-15243?

CVE-2026-15243 has a CVSS 4.0 base score of 7.4 (High). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N. EPSS exploitation probability: 0.2%.

Java Apereo Cas Client CVE-2026-15243

EUVD-2026-48560 HIGH

Improper Validation of Certificate with Host Mismatch (CWE-297)

2026-07-24 CERT-PL

GHSA-52jg-6vw4-42p8

Java Information Disclosure Microsoft Java Apereo Cas Client Jasig Cas Client Apereo

7.4

CVSS 4.0 · Vendor: CERT-PL

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Vulnerability Assessment

Weakness

CWE

CWE-297

OWASP Top 10:2025

A07:2025 - Authentication Failures

ASVS 5.0

V12 - Secure Communication Certificate host validation

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 26, 2026

Improper certificate validation in Apereo CAS Client 4.1.0 and Jasig CAS Client 3.6.4 allows a man-in-the-middle attacker to intercept Ticket-Granting Tickets (TGTs) by presenting any CA-signed certificate for a hostname matching the client's allowlist. An attacker with a network interception position can then obtain service tickets on behalf of the victim. No active exploitation or public exploit code is confirmed, and EPSS indicates low exploitation probability (0.17%).

Affected VersionsENISA

Java Apereo CAS Client 4.1.0

Jasig CAS Client 3.6.4

Affected Packages

euvd jasig_cas_client no fix

euvd java_apereo_cas_client no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in euvd

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (CERT-PL) PRIMARY 7.4 HIGH

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (CERT-PL) · only source for this CVE.

CVSS VectorVendor: CERT-PL

Attack Vector

Network

Attack Complexity

Low

Attack Requirements

Present

Privileges Required

None

User Interaction

Active

Vulnerable system: Confidentiality

High

Vulnerable system: Integrity

High

Vulnerable system: Availability

None

Subsequent system: Confidentiality

None

Subsequent system: Integrity

None

Subsequent system: Availability

None

DescriptionCVE.org

Apereo CAS Client accepts any CA-trusted certificate for any hostname, provided the URL the client is calling matches the configured allowlist or regex. An attacker with a MITM position (DNS poisoning, rogue Wi-Fi, malicious proxy, etc.) can provide any CA-signed certificate for a hostname that matches the configured allowlist or regex. This can lead to intercepting the CAS exchange, capturing the Ticket-Granting Ticket (TGT), and subsequently obtaining Service Tickets on behalf of the victim.

Because maintainers contact attempts were unsuccessful, vulnerabilities have only been confirmed in version 4.1.0 (Java Apereo CAS Client) and 3.6.4 (Jasig CAS Client) but may also affect other versions.

Threat Intelligence Overview

EPSS Score

0.2%

Top 93% exploitable

Social Media

Sightings

Data Quality

7 sources

Confidence: High

EUVD

NVD

CVE.org

EPSS

Vulnrichment CIRCL

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.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.2%

Patch available No

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation

None

System Exposure· derived

Open

Automatable

Human Impact· derived

Medium

Technical Impact

Partial

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +37

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.