CVE-2023-26207: Fortinet FortiProxy Information Disclosure

CVE-2023-26207 Overview

CVE-2023-26207 is an insertion of sensitive information into log file vulnerability affecting Fortinet FortiOS and FortiProxy products. This vulnerability allows an authenticated attacker to read certain passwords in plain text by accessing log files, potentially leading to credential theft and further network compromise.

Critical Impact

Authenticated attackers can extract plaintext passwords from log files, potentially enabling lateral movement, privilege escalation, or unauthorized access to additional network resources.

Affected Products

• Fortinet FortiOS versions 7.2.0 through 7.2.4
• Fortinet FortiProxy versions 7.0.0 through 7.0.10
• Fortinet FortiProxy versions 7.2.0 through 7.2.1

Discovery Timeline

• 2023-06-13 - CVE-2023-26207 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-26207

Vulnerability Analysis

This vulnerability is classified under CWE-532 (Insertion of Sensitive Information into Log File). The core issue stems from improper handling of sensitive data during logging operations within FortiOS and FortiProxy. When certain administrative or system operations are performed, password information is inadvertently written to log files in plaintext rather than being masked, hashed, or excluded from logging entirely.

An authenticated attacker with access to read system logs can extract these credentials and use them for malicious purposes. The network-based attack vector with low complexity requirements means that any authenticated user with log access permissions could potentially exploit this vulnerability.

Root Cause

The root cause of CVE-2023-26207 lies in insufficient data sanitization within the logging subsystem of FortiOS and FortiProxy. The affected components fail to properly filter or mask sensitive credential information before writing to log files. This is a common secure coding oversight where logging mechanisms capture full variable contents without implementing proper redaction of sensitive fields such as passwords, API keys, or authentication tokens.

Attack Vector

The attack vector for this vulnerability involves an authenticated user accessing log files through legitimate means. The attacker would:

1. Authenticate to the FortiOS or FortiProxy device with valid credentials
2. Navigate to or access system log files that contain sensitive information
3. Search log entries for plaintext password information
4. Extract the credentials for use in further attacks

Since the vulnerability requires authentication and log access, the attack surface is somewhat limited to users who already have some level of system access. However, this could include lower-privileged users who may not normally have access to sensitive credentials.

The vulnerability does not require user interaction and only affects confidentiality, as the attacker is reading existing logged information rather than modifying system data.

Detection Methods for CVE-2023-26207

Indicators of Compromise

• Unusual log file access patterns by authenticated users
• Bulk retrieval or export of system log files
• Access to log files by users who do not typically perform log review activities
• Evidence of credential reuse attacks following log access events

Detection Strategies

• Monitor and audit all access to system log files on FortiOS and FortiProxy devices
• Implement user behavior analytics to detect anomalous log access patterns
• Review authentication logs for credential use from unexpected sources following log access
• Deploy file integrity monitoring on log directories to detect unauthorized access

Monitoring Recommendations

• Enable detailed logging for administrative actions including log file access
• Configure SIEM alerts for bulk log file retrieval operations
• Implement regular reviews of user access permissions to log files
• Monitor for lateral movement or privilege escalation attempts that may indicate credential theft

How to Mitigate CVE-2023-26207

Immediate Actions Required

• Upgrade FortiOS to version 7.2.5 or later to address this vulnerability
• Upgrade FortiProxy to version 7.0.11 or later, or 7.2.2 or later
• Review and rotate any credentials that may have been exposed in log files
• Audit log access permissions and restrict to essential personnel only
• Review log files for any sensitive information that may have already been exposed

Patch Information

Fortinet has released security updates to address this vulnerability. Detailed patch information and remediation guidance is available in the FortiGuard Incident Response Advisory FG-IR-22-455. Organizations should prioritize upgrading to patched versions of FortiOS and FortiProxy to eliminate the risk of credential exposure through log files.

Workarounds

• Restrict log file access to only essential administrative personnel
• Implement network segmentation to limit access to management interfaces
• Enable multi-factor authentication to reduce the impact of potential credential theft
• Regularly rotate administrative credentials to limit the window of exposure
• Consider temporarily disabling verbose logging features if possible until patching can be completed

Organizations should implement these workarounds as interim measures while planning and executing the upgrade to patched versions. However, applying the official security patches remains the only complete remediation for this vulnerability.