CVE-2026-27868: Teldat Regesta Smart HD-PLC Disclosure Flaw

CVE-2026-27868 Overview

CVE-2026-27868 is an information disclosure vulnerability affecting the Teldat Regesta Smart HD-PLC industrial communications device. An unauthenticated remote attacker can query the device's /upgrade/query.php endpoint with the cmd=p+3&3Bversion parameter to retrieve privileged version information without any registration or authentication step. The flaw is tracked under [CWE-201: Insertion of Sensitive Information Into Sent Data]. Exposed version data enables attackers to fingerprint the device and identify additional exploitable weaknesses in the same firmware.

Critical Impact
Unauthenticated network attackers can extract privileged version information from the Regesta Smart HD-PLC TLDPH16D2 running firmware 11.02.05.10.02, enabling targeted follow-on attacks.

Affected Products

Teldat Regesta Smart HD-PLC
Model: TLDPH16D2
Firmware version: 11.02.05.10.02

Discovery Timeline

2026-06-17 - CVE-2026-27868 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2026-27868

Vulnerability Analysis

The Regesta Smart HD-PLC device exposes an upgrade query handler at /upgrade/query.php on its management interface. The handler responds to crafted cmd parameters without enforcing authentication or session validation. By submitting cmd=p+3&3Bversion, an attacker receives detailed version information that should only be accessible to administrators.

The disclosed data reveals firmware revision strings, build identifiers, and component versions. Attackers use this fingerprint to match the device against known firmware-specific vulnerabilities. The flaw is classified as [CWE-201] because sensitive internal data is included in responses sent to unauthenticated clients.

Teldat's Regesta Smart HD-PLC devices are deployed in utility and industrial control environments, where exposed management interfaces increase the risk profile. Additional technical context is available at the HackRTU CVE-2026-27868 Advisory.

Root Cause

The /upgrade/query.php endpoint fails to apply access control checks before processing the Version command. Authentication middleware is either missing or bypassed for this route. The handler treats unauthenticated callers identically to authenticated administrators when returning version metadata.

Attack Vector

The attack is performed over the network against the device's HTTP management interface. The attacker sends a single crafted GET request to /upgrade/query.php?cmd=p+3&3Bversion. No credentials, user interaction, or prior reconnaissance is required. The response contains the privileged version information directly.

Description of exploitation: an attacker locates an internet-reachable or network-reachable Regesta Smart HD-PLC, issues the crafted request to the upgrade query path, parses the version string returned, and uses it to plan subsequent attacks against the identified firmware build. See the HackRTU HRTU-0002 Advisory for additional details.

Detection Methods for CVE-2026-27868

Indicators of Compromise

HTTP GET requests to /upgrade/query.php containing the cmd=p+3 parameter or the version substring from unauthenticated sources.
Web server access logs on the device showing repeated probes to /upgrade/ paths without preceding authentication events.
Unusual external scanning activity targeting TCP ports exposed by Regesta Smart HD-PLC management interfaces.

Detection Strategies

Inspect device and upstream proxy logs for requests matching the pattern GET /upgrade/query.php?cmd=* and alert on those originating from non-management network segments.
Deploy network IDS signatures that flag HTTP requests to /upgrade/query.php containing version or cmd=p+3 parameters.
Correlate fingerprinting requests with subsequent firmware-specific exploit attempts against the same source IP.

Monitoring Recommendations

Forward HTTP access logs from Teldat Regesta Smart HD-PLC devices to a centralized SIEM or data lake for retention and correlation.
Establish baseline traffic patterns for the device management interface and alert on deviations involving /upgrade/ paths.
Monitor for outbound connections from operational technology (OT) segments that follow inbound /upgrade/query.php probes.

How to Mitigate CVE-2026-27868

Immediate Actions Required

Restrict network access to the Regesta Smart HD-PLC management interface using firewall rules or access control lists that permit only trusted administrative hosts.
Place affected devices behind a VPN or jump host and remove any direct internet exposure.
Contact Teldat support through the Teldat Global Support Portal to obtain remediation guidance for firmware 11.02.05.10.02.

Patch Information

No vendor patch is referenced in the published advisory at the time of CVE publication. Teldat customers should consult the Teldat Installation Guide and the Teldat Official Website for the latest firmware availability and security bulletins.

Workarounds

Block external access to the /upgrade/query.php path at the perimeter firewall or upstream reverse proxy until a vendor fix is available.
Segment HD-PLC devices into a dedicated OT VLAN and apply strict ingress filtering to the management interface.
Disable or filter the HTTP management interface entirely if the device is administered through an alternate, authenticated channel.

bash

# Example: block external access to the vulnerable path at an upstream reverse proxy
# nginx configuration snippet
location /upgrade/query.php {
    allow 10.0.0.0/24;     # trusted management subnet
    deny  all;
    proxy_pass http://regesta-device-internal;
}