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:

• Red Hat Security Advisory RHSA-2026:3189
• Red Hat Security Advisory RHSA-2026:3208
• Red Hat Security Advisory RHSA-2026:3379

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

# 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";)