CVE-2026-67596 in CSL 1010 M2M 3G WiFi Module
Summary
by MITRE • 07/30/2026
CSL 1010 M2M 3G WiFi Module firmware through 2.2.1.4 contains a weak encryption vulnerability that allows unauthenticated attackers to recover all stored secrets in plaintext by reversing a single-byte XOR cipher with a static key applied to the configuration backup file. Attackers can trivially decrypt the Router.cfg backup file to expose web administration and telnet passwords, WPA/WPA2 pre-shared keys, PPPoE and 3G/APN credentials, and SIM identifiers including IMSI and IMEI.
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Analysis
by VulDB Data Team • 07/30/2026
This vulnerability represents a critical cryptographic weakness in the CSL 1010 M2M 3G WiFi Module firmware version 2.2.1.4 and earlier, fundamentally undermining the security posture of connected industrial and IoT devices. The flaw stems from the implementation of a trivial single-byte XOR cipher with a static key that is applied to configuration backup files, specifically the Router.cfg file that contains all sensitive credentials and network parameters. This weakness directly maps to CWE-327, which addresses the use of weak or broken cryptographic algorithms, and more specifically to CWE-326, which focuses on inadequate encryption strength. The vulnerability exists in the device's firmware design where configuration data is stored using a deterministic encryption mechanism that lacks proper cryptographic security measures.
The operational impact of this vulnerability extends far beyond simple credential exposure, as it provides attackers with complete administrative access to the device and its network connectivity settings. When an attacker successfully decrypts the Router.cfg file through simple reverse engineering of the single-byte XOR cipher, they gain access to critical system information including web administration passwords that grant full control over the device's GUI interface, telnet credentials for command-line access, WPA/WPA2 pre-shared keys that allow network infiltration, PPPoE and 3G/APN credentials that provide internet connectivity, and SIM identifiers including IMSI and IMEI numbers that can be used for tracking and further targeting. This comprehensive credential exposure aligns with ATT&CK technique T1078 which covers valid accounts and T1566 which involves credential harvesting through various means.
The exploitability of this vulnerability is remarkably low for attackers due to the simplicity of the encryption mechanism, making it a prime target for automated exploitation tools in threat actor toolkits. The static nature of the XOR key means that once an attacker identifies the cipher pattern, they can decrypt any configuration backup file without requiring additional computational resources or time-consuming cryptanalysis. This vulnerability demonstrates poor security engineering practices and violates fundamental principles of secure configuration management as outlined in NIST SP 800-53 controls related to configuration management and cryptographic module security. Organizations deploying these devices face significant risk of unauthorized access, network infiltration, and potential data breaches since the exposed credentials can be used to establish persistent access points within networks.
Mitigation strategies should prioritize immediate firmware updates from vendors when available, though given the nature of this vulnerability, complete device replacement may be necessary if updates are not forthcoming. Network segmentation and access controls should be implemented to limit lateral movement even if attackers gain initial access through these credentials. Security monitoring should include detection of unusual network traffic patterns that might indicate exploitation attempts, particularly around configuration backup file access or authentication failures. Regular security assessments of IoT deployments should include inventory tracking of all connected devices and verification of their cryptographic implementations against established security standards. The vulnerability also underscores the importance of proper key management practices as specified in NIST SP 800-57 and highlights the need for secure-by-design principles in embedded systems development to prevent similar weaknesses from emerging in future device deployments.