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.
Published: 2026-10-01
Score: 9 Critical
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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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

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History

Fri, 02 Oct 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Thu, 01 Oct 2026 23:45:00 +0000

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'}


Subscriptions

Redhat Directory Server Enterprise Linux
cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-10-02T00:36:18.261Z

Reserved: 2026-09-07T09:14:21.954Z

Link: CVE-2026-86345

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-02T00:17:04.180

Modified: 2026-10-02T00:17:04.180

Link: CVE-2026-86345

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-10-01T00:00:00Z

Links: CVE-2026-86345 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-02T00:30:16Z

Weaknesses