CVE-2026-11786: 389 Directory Server Buffer Overflow Flaw

CVE-2026-11786 Overview

CVE-2026-11786 is an out-of-bounds read vulnerability in the 389 Directory Server, an enterprise-class Lightweight Directory Access Protocol (LDAP) server maintained by Red Hat. The LDAP Data Interchange Format (LDIF) parser reads past the end of a heap buffer when processing attribute types that contain trailing semicolons during a database import operation. The condition is classified under [CWE-125] Out-of-Bounds Read and is detectable under memory instrumentation tooling such as AddressSanitizer or Valgrind.

Critical Impact
An authenticated local administrator importing a crafted LDIF file can trigger a heap out-of-bounds read in 389-ds-base, exposing small amounts of adjacent heap memory during import.

Affected Products

389 Directory Server (389-ds-base)
Red Hat Directory Server distributions bundling the affected 389-ds-base package
LDAP deployments performing LDIF database import operations

Discovery Timeline

2026-06-09 - CVE-2026-11786 published to the National Vulnerability Database (NVD)
2026-06-09 - Last updated in NVD database

Technical Details for CVE-2026-11786

Vulnerability Analysis

The defect resides in the LDIF parsing routine used by 389-ds-base during database import. LDIF attribute descriptions follow the syntax attributeType[;option]*, where semicolons separate optional tags such as language codes or binary markers. When the parser encounters an attribute type that ends with a trailing semicolon but no subsequent option, the parser advances past the terminator and reads beyond the bounds of the allocated heap buffer.

The read does not modify memory, so the impact is limited to disclosure of adjacent heap contents to error logs, debug output, or memory instrumentation. The vulnerability requires local access and high privileges, because LDIF import is an administrative operation performed by directory operators or the dirsrv service account.

Root Cause

The root cause is missing bounds validation on the attribute-type token after a trailing semicolon is consumed. The parser uses pointer arithmetic to locate the next character without confirming that the pointer remains within the buffer terminated by a null byte. When the trailing semicolon sits adjacent to the buffer boundary, the next read dereferences memory outside the original allocation.

Attack Vector

Exploitation requires an attacker with high local privileges to supply a crafted LDIF file to the import process, for example through ldif2db, dsctl import, or equivalent administrative tooling. The vulnerability does not produce code execution or data modification. Confidentiality impact is limited to whatever heap bytes happen to follow the parsed buffer at the moment of import.

No public proof-of-concept exploit is published, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog. Verified technical detail is available in the Red Hat CVE-2026-11786 Advisory and Red Hat Bug Report #2485426.

Detection Methods for CVE-2026-11786

Indicators of Compromise

Unexpected segmentation faults, AddressSanitizer reports, or Valgrind Invalid read warnings emitted by ns-slapd or ldif2db processes during import
LDIF files containing attribute descriptions terminated with a trailing semicolon and no option value, for example cn;
Import operations launched by unprivileged or non-administrative accounts on the directory host

Detection Strategies

Audit LDIF files staged for import for malformed attribute descriptions before invoking ldif2db or dsctl import
Run pre-production imports under memory instrumentation to surface out-of-bounds reads in the parser
Correlate dirsrv error log entries referencing parser faults with the user identity that initiated the import

Monitoring Recommendations

Monitor execution of ldif2db, dsctl, and dsconf binaries through endpoint telemetry and Linux audit rules
Forward /var/log/dirsrv/slapd-*/errors to a centralized log platform and alert on crash signatures from the LDIF parser
Track file integrity for LDIF import directories to detect unauthorized staging of crafted input files

How to Mitigate CVE-2026-11786

Immediate Actions Required

Apply the 389-ds-base security update from your Linux distribution once available through Red Hat or downstream vendors
Restrict LDIF import operations to vetted administrators and remove unnecessary sudo rules granting access to directory tooling
Validate the structure of all LDIF input files before importing, rejecting attribute descriptions that end with a trailing semicolon

Patch Information

Red Hat tracks remediation under Red Hat CVE-2026-11786 Advisory and internal issue PSIRTSUPT-7600. Administrators should consult the vendor advisory for the fixed 389-ds-base package version applicable to their Red Hat Enterprise Linux release and apply it through dnf update 389-ds-base followed by a dirsrv service restart.

Workarounds

Sanitize LDIF files with a preprocessor that strips or rejects attribute descriptions ending in a trailing semicolon
Perform imports in an isolated staging instance before promoting data to production directory servers
Limit shell and service access to the dirsrv account so that only authorized operators can invoke import utilities

bash

# Configuration example: reject LDIF files containing trailing-semicolon attribute descriptions
grep -E '^[A-Za-z][A-Za-z0-9-]*;[[:space:]]*:' import.ldif && \
  echo "Malformed attribute description detected - aborting import" && exit 1

# Apply the vendor update and restart the directory service
sudo dnf update -y 389-ds-base
sudo systemctl restart dirsrv@<instance-name>