CVE-2026-25998: strongMan VPN Info Disclosure Flaw

CVE-2026-25998 Overview

CVE-2026-25998 is a cryptographic vulnerability affecting strongMan, the web-based management interface for strongSwan, an open-source IPsec-based VPN solution. The vulnerability stems from improper use of AES in Counter (CTR) mode encryption when storing sensitive credentials in the database, including private keys and EAP secrets. Due to the reuse of initialization vectors (IVs) across all encrypted database fields, attackers with database access can recover encrypted credentials by exploiting key stream reuse.

Critical Impact

Attackers with database access can decrypt sensitive VPN credentials including ECDSA private keys and EAP secrets, potentially compromising the entire VPN infrastructure's security posture.

Affected Products

• strongMan versions prior to 0.2.0
• strongSwan VPN deployments using affected strongMan management interfaces
• Systems storing encrypted credentials in strongMan's database

Discovery Timeline

• February 19, 2026 - CVE CVE-2026-25998 published to NVD
• February 19, 2026 - Last updated in NVD database

Technical Details for CVE-2026-25998

Vulnerability Analysis

This vulnerability falls under the category of broken cryptography (CWE-323: Reusing a Nonce, Key Pair in Encryption). When strongMan stores credentials such as private keys and EAP secrets in the database, it encrypts these fields using AES in CTR mode with a global database key. The fundamental cryptographic flaw lies in the absence of unique initialization vectors (IVs) for each encrypted value.

In AES-CTR mode, the security of the encryption depends critically on never reusing the same key and IV combination. When the same IV is used with the same key to encrypt multiple values, an identical key stream is generated for all encrypted data. This allows an attacker to perform XOR operations between ciphertext blocks to recover plaintext information without knowing the encryption key.

The situation is further exacerbated by the fact that certificates, which are considered public information, are encrypted using the same mechanism. An attacker can XOR the known plaintext of a certificate with its ciphertext to directly recover a substantial portion of the key stream. This recovered key stream can then be used to decrypt other secrets stored in the database, particularly shorter values like ECDSA private keys and EAP secrets.

Root Cause

The root cause of this vulnerability is the failure to generate individual, random initialization vectors for each database field encryption operation. strongMan's encryption implementation used a static or predictable IV across all encrypted database entries, violating the fundamental requirement of CTR mode that each encryption operation must use a unique nonce/IV combination.

Attack Vector

The attack requires an adversary to gain read access to the strongMan database. This could occur through:

• SQL injection vulnerabilities in related applications
• Database backup file exposure
• Compromised database credentials
• Insider threat with database access

Once database access is obtained, the attacker can exploit the IV reuse vulnerability through a known-plaintext attack. The attacker leverages the encrypted certificates (whose plaintext content is publicly known or easily obtained) to recover the key stream. By XORing the ciphertext of a certificate with its known plaintext, the attacker obtains the key stream bytes. These key stream bytes can then be applied to decrypt other encrypted fields that were encrypted with the same (reused) key stream, revealing ECDSA private keys and EAP secrets.

For detailed technical information about this cryptographic attack methodology, see the GitHub Security Advisory.

Detection Methods for CVE-2026-25998

Indicators of Compromise

• Unauthorized database read operations or queries targeting encrypted credential fields
• Unexpected access to strongMan database files or backups
• Evidence of database credential exfiltration in network logs
• Anomalous VPN authentication attempts using potentially compromised credentials

Detection Strategies

• Monitor database access logs for unusual SELECT queries targeting credential tables
• Implement database activity monitoring to detect bulk reads of encrypted fields
• Deploy file integrity monitoring on database backup locations
• Review strongMan version across all installations to identify vulnerable deployments

Monitoring Recommendations

• Enable comprehensive audit logging on the strongMan database
• Configure alerts for database access from unexpected IP addresses or user accounts
• Monitor for certificate-based authentication failures that may indicate key compromise
• Establish baseline patterns for normal database query activity to detect anomalies

How to Mitigate CVE-2026-25998

Immediate Actions Required

• Upgrade strongMan to version 0.2.0 or later immediately
• Audit database access logs for any unauthorized access attempts
• Rotate all VPN credentials (private keys and EAP secrets) stored in strongMan
• Review and revoke any certificates that may have been compromised

Patch Information

Version 0.2.0 of strongMan addresses this vulnerability by implementing a fundamentally improved encryption scheme. The fix switches from AES-CTR to AES-GCM-SIV encryption, which provides authenticated encryption with additional security guarantees. Each encrypted value now uses:

• A random nonce generated for each encryption operation
• An individually derived encryption key using HKDF (HMAC-based Key Derivation Function)

Database migrations are provided to automatically re-encrypt all existing credentials with the new secure encryption mechanism upon upgrade. For more details, refer to the GitHub Security Advisory.

Workarounds

• Restrict database access to the minimum required personnel and applications
• Implement network segmentation to limit database server exposure
• Enable encryption at rest for database storage as an additional layer
• Consider temporary offline storage of the most sensitive credentials until upgrade is complete

# Verify strongMan version and upgrade
pip show strongMan | grep Version
pip install --upgrade strongMan>=0.2.0

# After upgrade, verify the database migration completed successfully
# Check strongMan logs for migration status