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CVE-2026-15243— Improper Validation of Certificate in CAS Client

Quick assessment

Affected
Apereo Java Apereo CAS Client
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Apereo central authentication service是Apereo组织开源的一款单点登录认证服务系统。 Apereo Central Authentication Service 4.1.0版本和Jasig CAS Client 3.6.4版本存在加密问题漏洞，该漏洞源于接受任何CA信任的证书，可能导致具有中间人攻击位置的攻击者拦截CAS交换、捕获TGT并获取服务票据。

CVSS 7.4 · High EPSS 0.26% · P16

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle

Affected Version Matrix 2

VendorProduct Version RangeStatus
Apereo Jasig CAS Client 3.6.4 affected
Apereo Java Apereo CAS Client 4.1.0 affected
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I. Basic Information for CVE-2026-15243

Vulnerability Information
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Vulnerability Title
Improper Validation of Certificate in CAS Client
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
对宿主不匹配的证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Apereo Central Authentication Service 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Apereo central authentication service是Apereo组织开源的一款单点登录认证服务系统。 Apereo Central Authentication Service 4.1.0版本和Jasig CAS Client 3.6.4版本存在加密问题漏洞，该漏洞源于接受任何CA信任的证书，可能导致具有中间人攻击位置的攻击者拦截CAS交换、捕获TGT并获取服务票据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Apereo Java Apereo CAS Client 4.1.0 -
Apereo Jasig CAS Client 3.6.4 -

II. Public POCs for CVE-2026-15243

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III. Intelligence Information for CVE-2026-15243

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Security Blog Posts for CVE-2026-15243 (1)

Vendor Pages for CVE-2026-15243 (1)

IV. Related Vulnerabilities

Same vendor: Apereo
Same weakness: CWE-297

V. Comments for CVE-2026-15243

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