CVE-2025-14905: 389 Directory Server RCE Vulnerability

CVE-2025-14905 Overview

A heap buffer overflow vulnerability has been identified in the 389-ds-base directory server. The flaw exists in the schema_attr_enum_callback function within the schema.c file, where improper buffer size calculation leads to memory corruption when processing attribute aliases. This vulnerability occurs because the code sums alias string lengths without accounting for additional formatting characters required during processing. When a large number of aliases are processed, this miscalculation can trigger a heap overflow condition.

Critical Impact
Remote attackers can exploit this heap overflow to cause Denial of Service (DoS) or potentially achieve Remote Code Execution (RCE) on affected 389-ds-base directory servers.

Affected Products

389-ds-base directory server
Red Hat Enterprise Linux systems running 389-ds-base
Red Hat Directory Server deployments

Discovery Timeline

2026-02-23 - CVE-2025-14905 published to NVD
2026-02-25 - Last updated in NVD database

Technical Details for CVE-2025-14905

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow). The flaw manifests in the schema handling component of the 389-ds-base server, specifically within the schema_attr_enum_callback function. During attribute schema processing, the function allocates a buffer based on the combined length of alias strings. However, the calculation fails to include space for delimiter characters, separators, and null terminators that are added during the enumeration process.

When an attacker provides a schema definition with numerous aliases, the accumulated formatting overhead exceeds the allocated buffer space. This results in heap memory being overwritten beyond the intended boundary, corrupting adjacent heap metadata and potentially other critical data structures.

Root Cause

The root cause is an off-by-many error in buffer size calculation within schema.c. The schema_attr_enum_callback function iterates through attribute aliases and calculates the required buffer size by summing the strlen() of each alias. This calculation neglects to account for separator characters (such as commas or spaces) inserted between aliases and any prefix/suffix formatting characters required by the schema format. As the number of aliases increases, the deficit between allocated and required space grows, eventually causing a heap buffer overflow.

Attack Vector

This vulnerability is exploitable over the network by authenticated attackers with high privileges (based on the CVSS vector indicating PR:H). An attacker with administrative or schema modification privileges on the directory server can craft malicious schema entries containing excessive attribute aliases. When the server processes these schema definitions—either during schema replication, LDAP schema modification operations, or server restart with corrupted schema files—the vulnerable function is triggered.

The overflow can corrupt heap management structures, potentially leading to:

Immediate service crash (Denial of Service)
Controlled memory corruption enabling arbitrary code execution
Persistent DoS if malicious schema is stored and triggers on each server restart

Detection Methods for CVE-2025-14905

Indicators of Compromise

Unexpected crashes of the ns-slapd directory server process with heap corruption errors
Core dumps showing memory corruption in schema_attr_enum_callback or related schema functions
Abnormal LDAP schema modification attempts with unusually large numbers of attribute aliases
Server log entries indicating schema parsing failures or memory allocation errors

Detection Strategies

Monitor directory server logs for repeated crashes or memory-related error messages
Implement LDAP audit logging to track schema modification operations and identify suspicious activity
Deploy memory corruption detection tools (such as AddressSanitizer in test environments) to identify overflow conditions
Review schema entries for attributes with an unusually high number of aliases

Monitoring Recommendations

Configure alerting for ns-slapd process crashes and automatic restart events
Enable detailed LDAP access logging to capture schema modification requests
Monitor system memory usage and heap allocation patterns for the directory service
Implement file integrity monitoring on schema configuration files

How to Mitigate CVE-2025-14905

Immediate Actions Required

Apply the security patches provided in Red Hat Security Advisories immediately
Restrict schema modification privileges to only essential administrative accounts
Review existing schema definitions for attributes with excessive alias configurations
Consider temporarily disabling remote schema modification capabilities if patching is delayed

Patch Information

Red Hat has released security advisories addressing this vulnerability. Affected systems should be updated using the appropriate advisory:

Additional technical details are available in the Red Hat CVE Analysis for CVE-2025-14905 and Red Hat Bugzilla Report #2423624.

Workarounds

Limit schema modification privileges to only highly trusted administrators until patches can be applied
Implement network-level access controls to restrict LDAP administrative operations to trusted management networks
Deploy intrusion detection rules to identify and block LDAP requests with abnormally large schema definitions
Consider running the directory server in a containerized or sandboxed environment to limit the impact of potential exploitation

bash

# Restrict schema modification access via ACL configuration
# Add to your 389-ds-base configuration to limit schema write access
dn: cn=schema
changetype: modify
add: aci
aci: (targetattr = "*")(version 3.0; acl "Restrict Schema Modifications"; deny (write) userdn != "ldap:///uid=schema-admin,ou=admins,dc=example,dc=com";)