CVE-2026-24933 Overview
CVE-2026-24933 is an improper certificate validation vulnerability [CWE-295] in the API communication component of Asustor Data Master (ADM). The affected component fails to validate SSL/TLS certificates when issuing HTTPS requests to the server. An unauthenticated remote attacker positioned on the network path can perform a Man-in-the-Middle (MitM) attack and intercept cleartext communications. Exposed data includes account email addresses, MD5-hashed passwords, and device serial numbers.
Critical Impact
Network-adjacent attackers can intercept ADM API traffic and harvest credentials and device identifiers without authentication or user interaction.
Affected Products
- Asustor Data Master (ADM) 4.1.0 through 4.3.3.ROF1
- Asustor Data Master (ADM) 5.0.0 through 5.1.1.RCI1
- Asustor NAS devices running affected ADM firmware
Discovery Timeline
- 2026-02-03 - CVE-2026-24933 published to NVD
- 2026-02-19 - Last updated in NVD database
Technical Details for CVE-2026-24933
Vulnerability Analysis
The vulnerability resides in the ADM API communication component responsible for issuing HTTPS requests to backend servers. The client establishes TLS sessions without verifying the server certificate chain, hostname, or trust anchors. Any certificate, including self-signed or attacker-supplied certificates, is accepted as valid.
This defect collapses the confidentiality guarantee of TLS. An attacker on the same network segment, an upstream router, or a compromised Wi-Fi access point can terminate the TLS session, present a forged certificate, and proxy traffic to the legitimate server. The client proceeds with the handshake and transmits sensitive data over the attacker-controlled channel.
Root Cause
The root cause is missing or disabled certificate validation logic in the HTTPS client used by the ADM API component [CWE-295]. Common patterns that produce this defect include disabling hostname verification, supplying a permissive trust manager that accepts all certificates, or failing to invoke chain validation against the system trust store.
Attack Vector
Exploitation requires the attacker to occupy a network position between the ADM device and the remote server. Typical scenarios include ARP spoofing on a LAN, rogue Wi-Fi access points, compromised upstream infrastructure, or DNS poisoning. Once positioned, the attacker presents a forged TLS certificate and decrypts the proxied session. The intercepted payload reveals account emails, MD5-hashed password values suitable for offline cracking, and device serial numbers usable in follow-on attacks. The vulnerability is unauthenticated and requires no user interaction.
No public proof-of-concept code or exploit is available at the time of writing. See the Asustor Security Advisory #50 for vendor technical details.
Detection Methods for CVE-2026-24933
Indicators of Compromise
- Unexpected TLS certificates presented to ADM devices that do not chain to the legitimate Asustor service certificate authority.
- ARP table anomalies, duplicate MAC addresses, or unsolicited gratuitous ARP traffic on segments containing ADM devices.
- Outbound HTTPS connections from ADM devices to IP addresses that do not resolve to known Asustor infrastructure.
Detection Strategies
- Capture TLS handshakes from ADM devices and compare server certificate fingerprints against the known Asustor service certificate baseline.
- Inspect network flows for TLS sessions originating from ADM devices that terminate at non-Asustor ASN endpoints.
- Alert on DNS responses for Asustor service domains that resolve to private, residential, or unexpected ranges.
Monitoring Recommendations
- Enable certificate transparency monitoring for Asustor service domains and correlate observed certificates against device telemetry.
- Log all outbound connections from NAS devices at the network egress point and review for protocol or destination anomalies.
- Monitor authentication logs on associated accounts for credential reuse following any suspected interception event.
How to Mitigate CVE-2026-24933
Immediate Actions Required
- Upgrade ADM to a fixed release identified in Asustor Security Advisory #50.
- Rotate passwords on all accounts associated with affected ADM devices, prioritizing accounts with administrative privileges.
- Isolate ADM devices on a dedicated VLAN with restricted outbound access until patching is complete.
- Treat any MD5-hashed credentials previously transmitted by the device as compromised and force resets.
Patch Information
Asustor published remediation guidance in Asustor Security Advisory #50. Administrators should consult the advisory for the specific fixed ADM versions covering both the 4.x and 5.x branches and apply firmware updates through the ADM management interface.
Workarounds
- Restrict ADM device network egress to trusted networks only and block direct internet access where business requirements permit.
- Deploy network segmentation and 802.1X authentication to reduce the risk of attacker placement on the same broadcast domain.
- Disable or limit use of the affected API communication features until firmware updates are applied.
# Example: restrict ADM egress at the firewall (illustrative)
# Replace 192.0.2.10 with the ADM device address
iptables -I FORWARD -s 192.0.2.10 -p tcp --dport 443 -d <trusted_asustor_range> -j ACCEPT
iptables -A FORWARD -s 192.0.2.10 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
