CVE-2026-27895: LDAP Account Manager RCE Vulnerability

CVE-2026-27895 Overview

LDAP Account Manager (LAM) is a webfrontend for managing entries (e.g., users, groups, DHCP settings) stored in an LDAP directory. Prior to version 9.5, the PDF export component does not correctly validate uploaded file extensions. This inadequate validation allows any file type, including .php files, to be uploaded to the server. When combined with a related vulnerability (GHSA-w7xq-vjr3-p9cf), an attacker can achieve remote code execution as the web server user.

Critical Impact

Authenticated attackers can upload arbitrary file types including PHP scripts, potentially leading to remote code execution on vulnerable LAM installations.

Affected Products

• LDAP Account Manager (LAM) versions prior to 9.5

Discovery Timeline

• 2026-03-18 - CVE CVE-2026-27895 published to NVD
• 2026-03-18 - Last updated in NVD database

Technical Details for CVE-2026-27895

Vulnerability Analysis

This vulnerability is classified as CWE-185 (Incorrect Regular Expression), indicating that the file extension validation mechanism uses an improper regular expression pattern that fails to adequately restrict uploaded file types. The PDF export component in LDAP Account Manager is designed to handle document exports but lacks sufficient validation logic to prevent malicious file uploads.

The vulnerability exists in the network-accessible PDF export functionality and requires low-privileged authentication to exploit. While this vulnerability alone allows for unauthorized file uploads, its impact is amplified when chained with the related vulnerability documented in GHSA-w7xq-vjr3-p9cf, enabling full remote code execution under the web server user context.

Root Cause

The root cause lies in the incorrect regular expression used for file extension validation within the PDF export component. The flawed validation pattern does not properly restrict file extensions, allowing files with executable extensions such as .php to bypass security checks. This is a classic example of a blocklist approach failure where the validation regex fails to account for all potentially dangerous file types or bypass techniques.

Attack Vector

The attack requires network access to the LDAP Account Manager web interface and low-level authentication (authenticated user). An attacker can exploit this vulnerability by:

1. Authenticating to the LAM web interface with valid credentials
2. Navigating to the PDF export functionality
3. Uploading a malicious file with an executable extension (e.g., .php)
4. When combined with GHSA-w7xq-vjr3-p9cf, accessing the uploaded file to trigger remote code execution

The vulnerability allows modification of server files (integrity impact) but does not directly expose confidential data or cause service disruption. However, when chained with the related vulnerability, it enables full compromise of the web server.

Detection Methods for CVE-2026-27895

Indicators of Compromise

• Unexpected .php files or other executable scripts appearing in /var/lib/ldap-account-manager/config directory
• Web server logs showing unusual POST requests to the PDF export component with non-PDF file uploads
• Modified or new files with recent timestamps in LAM configuration directories
• Anomalous outbound network connections from the web server process

Detection Strategies

• Monitor file system changes in the /var/lib/ldap-account-manager/config directory for new or modified files
• Implement web application firewall (WAF) rules to detect and block file uploads with executable extensions
• Review web server access logs for suspicious patterns targeting the PDF export endpoint
• Enable file integrity monitoring (FIM) on LAM installation directories

Monitoring Recommendations

• Configure alerts for any new file creation in LAM configuration directories
• Implement log correlation to identify authentication followed by suspicious file upload activity
• Deploy endpoint detection and response (EDR) solutions to monitor web server process behavior
• Set up regular integrity checks comparing file hashes against known-good baselines

How to Mitigate CVE-2026-27895

Immediate Actions Required

• Upgrade LDAP Account Manager to version 9.5 or later immediately
• Apply the filesystem workaround if immediate upgrade is not possible
• Review system logs for any evidence of exploitation attempts
• Audit existing files in /var/lib/ldap-account-manager/config for unauthorized content

Patch Information

The vulnerability has been fixed in LDAP Account Manager version 9.5. Upgrading to this version or later is the recommended remediation. For detailed release information, see the GitHub Release Notes for 9.5. Additional security context is available in the GitHub Security Advisory GHSA-88hf-2cjm-m9g8.

Workarounds

• Make the /var/lib/ldap-account-manager/config directory read-only for the web server user to prevent malicious file uploads
• Restrict network access to the LAM web interface to trusted IP addresses only
• Implement additional access controls requiring multi-factor authentication for LAM administrative functions
• Deploy a reverse proxy with strict file upload filtering capabilities in front of the LAM installation

# Configuration example - Make config directory read-only for web server
# This prevents the web server user from writing files to the config directory
chmod -R a-w /var/lib/ldap-account-manager/config
chown -R root:root /var/lib/ldap-account-manager/config