Security Resilience

CVE-2023-28857

Info Disclosure in Apereo Central Authentication Service 6.5.0 – 6.5.9.1

Published
27 June 2023
Modified
21 November 2024
CVSS Score v3.1 4.0
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:N/A:N
EPSS Score 0.0050 42th percentile
Risk Priority 34 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2023-28857 is a medium-severity Exposure of Sensitive Information to an Unauthorized Actor (CWE-200) vulnerability in Apereo Central Authentication Service. Its CVSS base score is 4.0 (Medium).

Operationally, ranked at the 42th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

Apereo CAS is an open source multilingual single sign-on solution for the web. Apereo CAS can be configured to use authentication based on client X509 certificates. These certificates can be provided via TLS handshake or a special HTTP header, such…

more

as “ssl_client_cert”. When checking the validity of the provided client certificate, X509CredentialsAuthenticationHandler performs check that this certificate is not revoked. To do so, it fetches URLs provided in the “CRL Distribution Points” extension of the certificate, which are taken from the certificate itself and therefore can be controlled by a malicious user. If the CAS server is configured to use an LDAP server for x509 authentication with a password, for example by setting a “cas.authn.x509.ldap.ldap-url” and “cas.authn.x509.ldap.bind-credential” properties, X509CredentialsAuthenticationHandler fetches revocation URLs from the certificate, which can be LDAP urls. When making requests to this LDAP urls, Apereo CAS uses the same password as for initially configured LDAP server, which can lead to a password leak. An unauthenticated user can leak the password used to LDAP connection configured on server. This issue has been addressed in version 6.6.6. Users are advised to upgrade. There are no known workarounds for this vulnerability.

CWE(s)

Related Threats

CVEs Like This One

CVE-2025-3984Same product: Apereo Central Authentication Service
CVE-2023-4612Same product: Apereo Central Authentication Service
CVE-2024-11207Same product: Apereo Central Authentication Service
CVE-2025-3986Same product: Apereo Central Authentication Service
CVE-2024-11209Same product: Apereo Central Authentication Service
CVE-2024-11208Same product: Apereo Central Authentication Service
CVE-2025-3985Same product: Apereo Central Authentication Service
CVE-2024-4399Same product: Apereo Central Authentication Service
CVE-2025-54380Same vendor: Apereo
CVE-2025-61906Same vendor: Apereo

Affected Assets

apereo
central authentication service
6.5.0 — 6.5.9.1 · 6.6.0 — 6.6.6

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-200 CWE-522

Literacy training teaches users to recognize and avoid actions that result in unauthorized exposure of sensitive information.

addresses: CWE-200 CWE-522

Retaining and monitoring training records confirms personnel have completed privacy and security awareness training on handling sensitive data, reducing the chance of unauthorized exposure due to lack of knowledge.

addresses: CWE-200 CWE-522

Encrypting or otherwise protecting data at rest directly prevents unauthorized actors from reading sensitive information stored on disk or other media.

addresses: CWE-200 CWE-522

Out-of-band delivery transmits sensitive data on a separate path, directly reducing exposure to unauthorized actors on the primary channel.

addresses: CWE-200

Automated marking applies security attributes to system outputs, making it harder for attackers to exploit unmarked sensitive information leading to unauthorized exposure.

addresses: CWE-200

Proper attribute retention and permitted-value enforcement limits unauthorized actors from accessing sensitive information lacking correct labels.

addresses: CWE-200

Prevents unauthorized exposure of sensitive information by prohibiting untrusted external systems from processing or storing it.

addresses: CWE-200

By enforcing authorization matching prior to sharing, the control reduces the risk of exposing sensitive information to unauthorized actors.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

blocks

A.5.10 only requires awareness, a topic-specific acceptable-use policy stating expected behaviours/monitoring, and procedures referencing classification and other controls; per the owner's explicit rule on labelling and similar dependency-style clauses, this does not itself prevent exposure (CWE-200) unless access/DLP/etc. act on it.

blocks

Requiring the return of all physical and electronic assets plus secure deletion of organizational data from personal devices reduces the chance that sensitive information remains accessible to departing personnel.

blocks

A.5.12 only defines and communicates a classification scheme so that protection needs can be understood; per the owner's explicit rule, labeling/classification does not itself prevent exposure and requires other controls (e.g. access enforcement) to act on it.

blocks

By requiring classification labels and metadata on all information assets, the control makes it harder for sensitive data to be inadvertently exposed because downstream systems and users can recognize and enforce handling rules based on those labels.

blocks

Requiring encryption, access controls, and recipient authentication for transfers directly reduces the chance that sensitive data reaches an unauthorized observer.

blocks

Secure delivery, protected storage, and confidentiality of allocation records limit exposure of authentication material to unauthorized observers.

Hardening callouts derived

DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.

  • No fine-grained STIG row for CWE-200, a class-level weakness. Rules are authored against its narrower children: CWE-213, CWE-359, CWE-497, CWE-538, CWE-1295.
  • No fine-grained STIG row for CWE-522, a class-level weakness. Rules are authored against its narrower children: CWE-260, CWE-523.

References