Understanding and Defending Against CVE-2026-62645: Authentication Bypass in Reyrolle 7SR5

Overview

CVE-2026-62645 is a critical vulnerability affecting Siemens Reyrolle 7SR5 devices, specifically all versions prior to V2.70. This vulnerability allows an attacker to bypass authentication and gain unauthorized access to the device by exploiting information exposed through the web interface. The vulnerability has a CVSS score of 9.8, indicating a high severity level.

Understanding the Vulnerability / Threat

Root Cause Analysis

The root cause of CVE-2026-62645 is the exposure of information through the web interface that can be used to calculate current and past session ID numbers. This information disclosure allows an attacker to bypass authentication and gain unauthorized access to the device. The vulnerability belongs to the CWE-306 category, which involves authentication bypass.

Attack Surface & Vector

The attack surface for this vulnerability is the web interface of the Reyrolle 7SR5 device. An attacker can reach this vulnerability through a network-adjacent or remote unauthenticated attack vector. The preconditions needed are that the attacker must be able to access the web interface of the device.

Exploitation Mechanics — Scenario Walkthrough

Scenario: Compromising a Reyrolle 7SR5 Device 1. Initial Position: The attacker has network access to the Reyrolle 7SR5 device and can reach its web interface. 2. Triggering the Flaw: The attacker sends a crafted request to the web interface to exploit the information exposure vulnerability. This request is designed to gather information about current and past session ID numbers. 3. What Breaks: The security boundary that fails is the authentication mechanism. The exposed information allows the attacker to calculate valid session IDs, bypassing the need for legitimate authentication credentials. 4. Attacker's Prize: With a valid session ID, the attacker gains unauthorized access to the device. They can now perform actions that would typically require authentication, such as configuring the device, accessing sensitive information, or disrupting its operation.

Real-World Impact

The potential impact of CVE-2026-62645 is significant. An attacker could use this vulnerability to gain control over the Reyrolle 7SR5 device, potentially disrupting critical infrastructure or industrial processes. This could lead to data theft, lateral movement within a network, or even ransomware deployment.

Detection & Defense

Immediate Mitigations

To address CVE-2026-62645, Siemens recommends upgrading Reyrolle 7SR5 devices to version V2.70 or later. This patch likely addresses the information exposure vulnerability and prevents session ID calculation.

Detection Strategies

Defenders can detect exploitation attempts by monitoring web interface logs for unusual or suspicious requests that may indicate an attempt to gather session ID information. Implementing a web application firewall (WAF) with rules to detect and block such requests can also be effective. MITRE ATT&CK techniques related to this vulnerability include T1190 (Exploit Public-Facing Application) and T1078 (Valid Accounts).

Long-Term Hardening

To prevent similar vulnerabilities, it's essential to implement secure coding practices, such as secure session ID generation and management, and robust authentication mechanisms. Regular security audits and penetration testing can help identify and address potential vulnerabilities before they are exploited.

Key Takeaways

* CVE-2026-62645 is a critical vulnerability in Siemens Reyrolle 7SR5 devices that allows authentication bypass. * The vulnerability is caused by information exposure through the web interface. * Upgrading to version V2.70 or later is the recommended mitigation. * Detection strategies include monitoring web interface logs and implementing a WAF. * Secure coding practices and regular security audits are essential for preventing similar vulnerabilities.

Sources

* National Vulnerability Database (NVD) - CVE-2026-62645 * Siemens Security Advisories