dbcve.org
Enterprise LinuxOperating system · Redhat

CVE-2018-16838

MEDIUM · 5.4 CVSS v3.0 Published 2019-03-25
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
60/100
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
A flaw was found in sssd Group Policy Objects implementation. When the GPO is not readable by SSSD due to a too strict permission settings on the server side, SSSD will allow all authenticated users to login instead of denying access.

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

In SSSD's Group Policy Objects implementation, when GPO files cannot be read due to overly strict server-side permissions, SSSD exhibits fail-open behavior by allowing all authenticated users to log in rather than properly denying access. This creates an unintended security bypass where access control decisions are incorrectly relaxed when GPO metadata is inaccessible.

MitigationEnsure GPO files and directories on the server have proper read permissions configured for the SSSD service account, allowing SSSD to successfully retrieve and enforce Group Policy settings instead of falling back to permissive access.

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
Enterprise LinuxOperating system
Affected:= 7.0
SssdApplication
Affected:all versions

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
Low
Integrity
Low
Availability
None

CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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. Verify SSSD is installed
    Run 'rpm -qa | grep -i sssd' or 'dpkg -l | grep -i sssd' depending on distribution
    Affected if SSSD package is not installed - the system is not affected by this vulnerability
  2. Check if GPO access control is enabled in SSSD config
    Inspect /etc/sssd/sssd.conf and look for parameters like 'ad_gpo_access_control', 'ldap_id_mapping', or 'gpo' related settings
    Affected if GPO-based access control is enabled (ad_gpo_access_control set to 'enforcing' or similar) - the system could be affected if GPO files are inaccessible
  3. Identify GPO-related SSSD service
    Run 'sssctl config-check' or check sssd logs in /var/log/sssd/ for 'gpo' or 'ad_gpo' related entries
    Affected if GPO functionality is actively being used by SSSD - the fail-open condition could apply
  4. Check GPO file permissions on the server
    Verify read permissions on Group Policy files and directories on the domain controller or sysvol share that SSSD accesses. Use 'ls -la' on the SYSVOL path or check SMB/CIFS mount permissions
    Affected if GPO files or directories lack read permission for the SSSD service account - this triggers the fail-open behavior described in the CVE
  5. Review SSSD access control logs
    Examine /var/log/sssd/sssd_*.log files for access control decisions. Look for messages about GPO retrieval failures or fallback to permissive access
    Affected if Logs show GPO retrieval failures followed by permissive access grants - the system is experiencing the vulnerability condition

A system is affected if it uses SSSD with GPO-based access control and the GPO files are inaccessible to SSSD, causing it to grant access to all authenticated users instead of properly denying access.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Ensure GPO files and directories on the server have proper read permissions configured for the SSSD service account, allowing SSSD to successfully retrieve and enforce Group Policy settings instead of falling back to permissive access.

Fix this in Enterprise Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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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-2018-16838 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

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