CVE-2026-86345

389-ds-base: 389-ds-base: starttls plaintext-buffer retention allows on-path attacker to forge an ldap client's authentication result

Published Oct 1, 2026 CVSS 3.1 · 9 Critical EPSS < 1% KEV · Not listed
Description
A flaw was found in 389-ds-base. The server does not discard plaintext bytes already buffered from a client connection when negotiating StartTLS, allowing an on-path attacker to inject a crafted LDAP message that is processed after the TLS upgrade and whose response is delivered to the client in place of the client's own pending operation's response, due to messageID collision. This can cause a client application to treat a failed authentication (bind) attempt as successful.

Remediation

Vendor Workaround

Disable StartTLS on port 389 and require ldaps:// (port 636) instead, which has no cleartext prefix to inject into. No configuration-only mitigation fully closes the issue on port 389 while StartTLS remains enabled.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Redhat rhel Els
CPEs 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
cpe:/a:redhat:enterprise_linux:10
cpe:/a:redhat:enterprise_linux:8
cpe:/a:redhat:enterprise_linux:9
cpe:/o:redhat:rhel_els:6
cpe:/o:redhat:rhel_els:7
Vendors & Products Redhat rhel Els
Type Values Removed Values Added
First Time appeared Redhat redhat Directory Server
Vendors & Products Redhat redhat Directory Server
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description A flaw was found in 389-ds-base. The server does not discard plaintext bytes already buffered from a client connection when negotiating StartTLS, allowing an on-path attacker to inject a crafted LDAP message that is processed after the TLS upgrade and whose response is delivered to the client in place of the client's own pending operation's response, due to messageID collision. This can cause a client application to treat a failed authentication (bind) attempt as successful.
Title 389-ds-base: 389-ds-base: starttls plaintext-buffer retention allows on-path attacker to forge an ldap client's authentication result
First Time appeared Redhat
Redhat directory Server
Redhat enterprise Linux
Weaknesses CWE-923
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': 9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 7, 2026, 5:01 AM
Reserved
Sep 7, 2026, 9:14 AM
Status
Awaiting Analysis
Published
Oct 2, 2026, 12:17 AM
Modified
Nov 6, 2026, 1:18 AM
Severity
Moderate
Public date
Oct 1, 2026, 12:00 AM