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Ucs\@schoolApplication · Univention

CVE-2020-17477

MEDIUM · 6.5 CVSS v3.1 Published 2023-10-26
Fix available
A fix is available. Upgrade to after 4.4 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Incorrect LDAP ACLs in ucs-school-ldap-acls-master in UCS@school before 4.4v5-errata allow remote teachers, staff, and school administrators to read LDAP password hashes (sambaNTPassword, krb5Key, sambaPasswordHistory, and pwhistory) via LDAP search requests. For example, a teacher can gain administrator access via an NTLM hash.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The ucs-school-ldap-acls-master component in UCS@school prior to version 4.4v5-errata contains improperly configured LDAP Access Control Lists that grant teacher, staff, and school administrator roles unauthorized read access to sensitive password hash attributes (sambaNTPassword, krb5Key, sambaPasswordHistory, pwhistory) through standard LDAP search queries.

MitigationCorrect the LDAP ACLs in ucs-school-ldap-acls-master to deny read access to password hash attributes for teacher, staff, and school administrator accounts while preserving legitimate access for privileged accounts.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Ucs\@schoolApplication
Affected:<= 4.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if UCS@school is installed
    Run 'univention-app list' or check for ucs-school-ldap-acls-master package with 'dpkg -l | grep ucs-school-ldap-acls-master' or 'rpm -qa | grep ucs-school-ldap-acls-master'
    Affected if The ucs-school-ldap-acls-master package is present and version is 4.4 or lower
  2. Identify the UCS@school version
    Check /etc/univention/release or run 'ucr get version/version' to determine if the version is 4.4 or below
    Affected if The installed version is 4.4 or any version prior to 4.4v5-errata
  3. Locate the LDAP ACL configuration file
    Look for the ucs-school-ldap-acls-master configuration in /etc/ldap/slapd.conf or under /etc/univention/templates/, or check the UDM LDAP ACLs via 'univention-admin ldapACL'
    Affected if The LDAP ACL configuration file exists and contains entries for ucs-school-ldap-acls-master
  4. Inspect ACL rules for password hash attributes
    Examine the ACL configuration for entries containing sambaNTPassword, krb5Key, sambaPasswordHistory, or pwhistory attributes and check which roles (teacher, staff, school administrator) are granted read access
    Affected if ACL rules explicitly grant teacher, staff, or school administrator roles read (auth or search) access to any of these password hash attributes
  5. Test actual LDAP access as a non-privileged role
    Perform an LDAP search as a teacher, staff, or school administrator account querying for password hash attributes: 'ldapsearch -x -D "uid=teacheruser,cn=teachers,ou=schools,dc=domain" -W -b "cn=users,dc=domain" "(objectClass=person)" sambaNTPassword krb5Key'
    Affected if The search returns values for sambaNTPassword, krb5Key, or other password hash attributes for users outside the privileged groups

A system is affected if UCS@school version 4.4 or lower is running with ucs-school-ldap-acls-master installed and the LDAP ACLs grant teacher, staff, or school administrator roles read access to password hash attributes.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 4.4
Interim mitigation

Correct the LDAP ACLs in ucs-school-ldap-acls-master to deny read access to password hash attributes for teacher, staff, and school administrator accounts while preserving legitimate access for privileged accounts.

Recommended fix Moderate confidence

UCS@school 4.4v5-errata or later

  1. 1. Back up the current UCS@school configuration and LDAP directory
  2. 2. Update the package repository to ensure latest errata are available: `univention-updater` or `apt-get update`
  3. 3. Upgrade UCS@school to version 4.4v5-errata or later using the standard UCS update mechanism
  4. 4. Verify the ldap-acls have been updated by checking the /etc/ldap/slapd.conf or running `univention-ldapsearch` with a teacher account to confirm password hashes are no longer visible
  5. 5. Test that teachers, staff, and school administrators can no longer retrieve sambaNTPassword, krb5Key, sambaPasswordHistory, or pwhistory attributes via LDAP searches
Caveat Standard UCS upgrade precautions apply - test in staging environment first, ensure backups are verified

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ucs\@school Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,330
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-17477 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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