CVE-2023-28857
Info Disclosure in Apereo Central Authentication Service 6.5.0 – 6.5.9.1
Raw vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:N/A:NSummary
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, exploitation aligns with the MITRE ATT&CK technique Unsecured Credentials (T1552); ranked at the 40th 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
- 🇪🇺 ENISA EUVD: EUVD-2024-2624
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…
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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
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 8 hardening rules · 6 OS baselines
V10.4.9V11.7.1V14.1.2V14.2.4
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.
Literacy training teaches users to recognize and avoid actions that result in unauthorized exposure of sensitive information.
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.
Encrypting or otherwise protecting data at rest directly prevents unauthorized actors from reading sensitive information stored on disk or other media.
Out-of-band delivery transmits sensitive data on a separate path, directly reducing exposure to unauthorized actors on the primary channel.
Automated marking applies security attributes to system outputs, making it harder for attackers to exploit unmarked sensitive information leading to unauthorized exposure.
Proper attribute retention and permitted-value enforcement limits unauthorized actors from accessing sensitive information lacking correct labels.
Prevents unauthorized exposure of sensitive information by prohibiting untrusted external systems from processing or storing it.
By enforcing authorization matching prior to sharing, the control reduces the risk of exposing sensitive information to unauthorized actors.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Encrypting data-at-rest fully prevents insecure credential storage while only partially satisfying the broader data-protection outcome.
Encrypting data-in-transit fully prevents interception of credentials in motion while only partially satisfying the broader data-protection outcome.
Credential management practices directly reduce insecure storage/transmission but do not guarantee encryption or transport protection.
Protecting identity assertions covers conveyance of credentials but is narrower than full credential lifecycle protection.
PR.AA-05 directly enforces least-privilege authorization that blocks most unauthorized disclosures, yet CWE-200 also arises from logging, error messages, and side-channel paths that access controls alone do not address.
PR.DS-10 mostly prevents CWE-200 by directly eliminating unauthorized access to sensitive data-in-use, yet only partially addresses the weakness because CWE-200 spans many other exposure vectors outside runtime protection.
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.
Restricting anonymous or unknown access and encrypting high-value information limits the exposure of sensitive data that would otherwise be obtainable by unauthorized actors.
Suppressing system details, error specifics, and previous log-on information until successful authentication reduces the information an unauthenticated attacker can gather.
By requiring owners to assign sensitivity labels and corresponding handling rules, the control ensures that information is not left unmarked and therefore reduces the chance that sensitive data will be exposed to unauthorized actors.
Requiring encryption, access controls, and recipient authentication for transfers directly reduces the chance that sensitive data reaches an unauthorized observer.
Secure delivery, protected storage, and confidentiality of allocation records limit exposure of authentication material to unauthorized observers.
Requiring defined procedures, assigned roles, and technical/organizational measures for handling PII reduces the chance that sensitive personal data will be exposed to unauthorized actors through inadequate handling or missing safeguards.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Ubuntu 22.04 (1 rule)
- V-260470 Ubuntu 22.04 LTS, when booted, must require authentication upon booting into single-user and maintenance modes. prevents CWE-200
Ubuntu 24.04 (2 rules)
- V-270647 Ubuntu 24.04 LTS must not have the telnet package installed. prevents CWE-200
- V-270675 Ubuntu 24.04 LTS when booted must require authentication upon booting into single-user and maintenance modes. prevents CWE-200
Windows 10 (1 rule)
- V-220737 Administrative accounts must not be used with applications that access the Internet, such as web browsers, or with potential Internet sources, such as email. prevents CWE-200
Windows Server 2016 (1 rule)
- V-224974 Domain-created Active Directory Organizational Unit (OU) objects must have proper access control permissions. prevents CWE-200
Windows Server 2019 (1 rule)
- V-205743 Windows Server 2019 organization created Active Directory Organizational Unit (OU) objects must have proper access control permissions. prevents CWE-200
Windows Server 2022 (1 rule)
- V-254395 Windows Server 2022 organization created Active Directory Organizational Unit (OU) objects must have proper access control permissions. prevents CWE-200