Information disclosure in Apereo Cas
CVE-2023-28857
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 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.
Vulnerability class: Information Disclosure
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.005 (40.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 41st percentile — 40.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- Apereo Cas — versions >= 6.5.0, < 6.5.9.1, >= 6.6.0, < 6.6.6
- Apereo Central Authentication Service
Weakness classification (CWE)
References
- securitylab.github.com/advisories/GHSL-2023-009_Apereo_CAS/ (Third Party Advisory)
- apereo.github.io/2023/02/20/x509-vuln/ (Third Party Advisory)
- github.com/apereo/cas/releases/tag/v6.6.6 (Release Notes)
Frequently asked questions
- What is CVE-2023-28857?
- CVE-2023-28857 is a medium-severity vulnerability in Apereo Cas, classified under Information Disclosure. CVSS score: 4.0/10. Published 2023-06-27.
- How severe is CVE-2023-28857?
- Medium severity. CVSS v3 base score is 4.0 out of 10.