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.

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Fixes

Solution

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Workaround

Restrict network access to the LDAP port (389/tcp, 636/tcp) to trusted networks only using firewall rules or network ACLs. This prevents untrusted remote attackers from reaching the vulnerable code path. Optionally, lower the nsslapd-maxbersize configuration parameter to reduce the maximum BER message size accepted by the server. Note that this caps bytes, not the number of controls, and does not fully eliminate the amplification. Setting it too low may impact legitimate LDAP operations with large payloads.

History

Wed, 20 May 2026 10:00:00 +0000

Type Values Removed Values Added
Description 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.
Title 389-ds-base: 389-ds-base: unbounded ldap controls count in get_ldapmessage_controls_ext() causes cpu and heap amplification (remote dos)
First Time appeared Redhat
Redhat directory Server
Redhat enterprise Linux
Weaknesses CWE-770
CPEs cpe:/a:redhat:directory_server:11
cpe:/a:redhat:directory_server:12
cpe:/a:redhat:directory_server:13
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat directory Server
Redhat enterprise Linux
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-05-20T09:00:42.557Z

Reserved: 2026-05-20T08:19:21.037Z

Link: CVE-2026-9064

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-05-20T10:16:28.940

Modified: 2026-05-20T10:16:28.940

Link: CVE-2026-9064

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-20T11:30:26Z

Weaknesses