CVE-2026-105156: YzmCMS Privilege Escalation Vulnerability

CVE-2026-105156 Overview

CVE-2026-105156 affects YzmCMS versions up to 7.6. The flaw resides in the Password function within /common/function/system.func.php, part of the MD5 Handler component. The function derives password hashes with insufficient computational effort, allowing an attacker who obtains stored hashes to recover plaintext credentials through offline cracking. The weakness is classified under CWE-326: Inadequate Encryption Strength. The vendor has stated that a backward-compatible gradual hash migration feature will be included in the release scheduled for March 2027. Public exploit material is referenced in the VulDB submission.

Critical Impact
Stored YzmCMS user password hashes can be reversed to plaintext credentials once exfiltrated, enabling account takeover and lateral access to administrative functions.

Affected Products

YzmCMS versions up to and including 7.6
Component: MD5 Handler within /common/function/system.func.php
Function: Password

Discovery Timeline

2026-10-04 - CVE-2026-105156 published to the National Vulnerability Database (NVD)
2026-10-06 - Last updated in the NVD database
March 2027 - Vendor-scheduled release that will introduce gradual hash migration

Technical Details for CVE-2026-105156

Vulnerability Analysis

The Password function in /common/function/system.func.php processes the pass argument and returns a password representation that uses a hashing scheme with insufficient computational cost. Modern password storage requires adaptive, slow key-derivation functions such as bcrypt, scrypt, or argon2id. By relying on an MD5-based routine, YzmCMS produces hashes that can be computed at billions of operations per second on commodity GPUs. An attacker who obtains the password database through a secondary vulnerability or backup disclosure can reverse those hashes offline. The vendor acknowledges the issue and plans a migration feature for the March 2027 release.

Root Cause

The root cause is the selection of MD5 as the password-hashing primitive without stretching, work factor, or memory-hard construction. MD5 is a general-purpose cryptographic digest designed for speed, which is the opposite of what password storage requires. The implementation does not apply iterative hashing or an adequate per-user salt-plus-work-factor scheme, falling under CWE-326.

Attack Vector

Exploitation is remote in the sense that the resulting hashes can be attacked offline after the attacker obtains the credential store. The attack complexity is high because it depends on first acquiring the hash material and then performing cracking against the recovered digests. Once hashes are retrieved, dictionary and brute-force attacks against the Password output can recover plaintext credentials for administrator and user accounts. Successful recovery enables authenticated access to the YzmCMS backend.

No verified exploit code is available. Refer to the GitHub Issue Discussion and VulDB CVE Details for technical context.

Detection Methods for CVE-2026-105156

Indicators of Compromise

Unexpected read access to /common/function/system.func.php or database tables containing user credentials.
Successful administrative logins from new or geographically improbable source addresses following a database export event.
Database dump files appearing in web-accessible directories or backup locations.

Detection Strategies

Review application and web server logs for bulk access patterns against user tables or credential endpoints.
Alert on authentication events that follow suspicious file read activity on YzmCMS source files or database backups.
Hunt for offline-cracking indicators such as sudden successful logins for accounts that have been dormant.

Monitoring Recommendations

Monitor for unauthorized changes to /common/function/system.func.php and related YzmCMS source files.
Track egress traffic volume from the database host to detect credential store exfiltration.
Enable auditing on administrative actions in YzmCMS and alert on privilege changes.

How to Mitigate CVE-2026-105156

Immediate Actions Required

Enforce strong password policies on all YzmCMS accounts to raise the cost of offline cracking.
Enable multi-factor authentication at the reverse-proxy or application layer wherever supported.
Restrict access to the YzmCMS administration interface by source IP address or VPN.
Audit stored credentials and rotate passwords for privileged accounts.

Patch Information

As of publication, no patched release is available. The vendor has committed to a backward-compatible gradual hash migration feature in the YzmCMS release scheduled for March 2027. Interim security mitigation guidance is to be published on the official YzmCMS documentation. Monitor the GitHub Issue Discussion for updates.

Workarounds

Protect the credential store by restricting file-system and database access to the minimum required service accounts.
Place the YzmCMS application behind a web application firewall and block anomalous query patterns against user tables.
Disable or remove unused administrative accounts to reduce the exposed credential surface.
Encrypt database backups and store them outside the web root with strict access controls.

bash

# Example: restrict database file access and backups to the service user
chown mysql:mysql /var/lib/mysql -R
chmod 700 /var/lib/mysql

# Move YzmCMS database backups outside the web root
mv /var/www/yzmcms/backup /var/backups/yzmcms
chmod 600 /var/backups/yzmcms/*.sql