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Directory ServerApplication · Redhat

CVE-2026-9064

HIGH · 7.5 CVSS v3.1 Published 2026-05-20
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges 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 389-ds-base. The get_ldapmessage_controls_ext() function in the LDAP server does not enforce an upper bound on the number of controls per LDAP message. A remote, unauthenticated attacker can send a specially crafted LDAP request containing hundreds of thousands of minimal controls within the default maximum BER message size (2 MB), causing excessive CPU consumption and heap allocation on the server. Under concurrent exploitation, this leads to significant latency degradation, worker thread starvation, or out-of-memory termination, resulting in a denial of service.

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 get_ldapmessage_controls_ext() function in 389-ds-base lacks validation to limit the number of controls per LDAP message. An attacker can embed hundreds of thousands of minimal controls within the 2 MB BER message size limit, exhausting CPU and heap memory.

MitigationImplement an upper bound check on the number of controls in get_ldapmessage_controls_ext() to reject requests exceeding a reasonable threshold (e.g., a few dozen controls).

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
Directory ServerApplication
Affected:= 11.0= 12.0= 13.0
389 Directory ServerOperating system
Affected:all versions
Enterprise LinuxOperating system
Affected:= 6.0= 7.0= 8.0= 9.0= 10.0

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
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

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 389-ds-base package is installed
    Check for the presence of the 389-ds-base package. On RHEL-based systems, run: rpm -qa | grep 389-ds-base
    Affected if The 389-ds-base package is found on the system
  2. Check installed version against affected ranges
    Run 'rpm -q 389-ds-base' or 'dnf list installed 389-ds-base' to obtain the exact version, then compare to the affected versions: 11.0, 12.0, 13.0 for Redhat Directory Server, or any version for Redhat 389 Directory Server
    Affected if The installed version matches 11.0, 12.0, 13.0, or is any version of Redhat 389 Directory Server
  3. Confirm LDAP service is exposed
    Check if the LDAP server is listening on ports 389 or 636. Run: ss -tlnp | grep -E ':(389|636)\s' or netstat -tlnp | grep -E ':(389|636)'
    Affected if The LDAP ports 389 or 636 are open and listening, making the server remotely accessible
  4. Inspect for worker thread starvation or high memory usage
    Monitor for signs of the DoS condition: check process memory usage (ps aux | grep ns-slapd), look for worker thread blockages in /var/log/dirsrv/slapd-*/errors, or observe system OOM killer activity in /var/log/messages
    Affected if The server exhibits excessive memory consumption, worker thread blocking, or OOM events that correlate with LDAP requests containing many controls

A system is affected if it runs any version of 389-ds-base (versions 11.0, 12.0, 13.0, or all versions of Redhat 389 Directory Server) with LDAP ports exposed, and exhibits symptoms of resource exhaustion from processing many controls per LDAP message.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement an upper bound check on the number of controls in get_ldapmessage_controls_ext() to reject requests exceeding a reasonable threshold (e.g., a few dozen controls).

Recommended fix Moderate confidence

Obtain the fixed version from Red Hat security advisory (access.redhat.com)

  1. Contact Red Hat at access.redhat.com to obtain the specific security advisory for this vulnerability
  2. Request the CVE-2026-9066 patch/advisory for 389-ds-base
  3. Apply the vendor-supplied update via 'yum update 389-ds-base' or 'dnf update 389-ds-base'
  4. Restart the directory server service after applying the update
  5. Verify the server is operational and controls are properly limited
Caveat Minor - this is a security fix; review release notes for any configuration changes

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

Fix this in Directory Server Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,760
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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-2026-9064 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
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data