CVE-2018-7356 in ZXR10 8905E
Summary
by MITRE
All versions up to V3.03.10.B23P2 of ZTE ZXR10 8905E product are impacted by TCP Initial Sequence Number (ISN) reuse vulnerability, which can generate easily predictable ISN, and allows remote attackers to spoof connections.
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Analysis
by VulDB Data Team • 04/09/2020
The TCP Initial Sequence Number (ISN) reuse vulnerability identified as CVE-2018-7356 affects ZTE ZXR10 8905E network equipment running firmware versions up to V3.03.10.B23P2. This vulnerability represents a critical weakness in the network device's TCP stack implementation that fundamentally compromises connection security and integrity. The flaw stems from the predictable generation of sequence numbers during TCP connection establishment, which violates fundamental security principles for network communications. According to CWE-1244, this vulnerability falls under the category of weak random number generation in cryptographic contexts, making it particularly dangerous for network infrastructure devices.
The technical implementation of this vulnerability involves the device's failure to properly randomize TCP initial sequence numbers across different connections. When a TCP connection is established, each side generates an initial sequence number that should be unpredictable to prevent connection spoofing attacks. However, in affected ZTE devices, the ISN generation algorithm produces predictable values that can be easily guessed by remote attackers. This predictable pattern allows malicious actors to inject packets into existing TCP sessions without proper authentication, effectively enabling man-in-the-middle attacks and session hijacking. The vulnerability operates at the transport layer of the OSI model and specifically targets the TCP protocol's connection establishment mechanism.
The operational impact of this vulnerability extends beyond simple connection spoofing, as it can enable complete network compromise of affected devices. Attackers can exploit this weakness to intercept, modify, or terminate legitimate network communications, potentially leading to data breaches, service disruption, and unauthorized access to network resources. The vulnerability affects network infrastructure components that rely on TCP for communication protocols, making it particularly dangerous for enterprise networks and service provider environments. According to ATT&CK framework tactic TA0011 (Command and Control), this vulnerability could be leveraged for establishing persistent access to target networks through covert communication channels. The predictable ISN also enables attackers to perform TCP reset attacks, allowing them to disrupt services or redirect traffic to malicious endpoints.
Mitigation strategies for CVE-2018-7356 should prioritize immediate firmware upgrades to versions that address the ISN generation weakness. Network administrators must ensure that all affected ZTE ZXR10 8905E devices are updated to the latest secure firmware releases provided by ZTE. Additionally, implementing network segmentation and access controls can help limit the potential impact of exploitation. Security monitoring should be enhanced to detect unusual TCP connection patterns that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper entropy sources in network protocol implementations and aligns with security best practices outlined in NIST SP 800-90A for cryptographic random number generation. Organizations should also consider implementing TCP sequence number randomization at the network level through firewall rules or network security appliances to provide additional protection against exploitation attempts.