CVE-2023-34367 in Windows
Summary
by MITRE • 06/14/2023
Windows 7 is vulnerable to a full blind TCP/IP hijacking attack. The vulnerability exists in Windows 7 (any Windows until Windows 8) and in any implementation of TCP/IP, which is vulnerable to the Idle scan attack (including many IoT devices). NOTE: The vendor considers this a low severity issue.
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Analysis
by VulDB Data Team • 01/07/2026
The vulnerability identified as CVE-2023-34367 represents a critical flaw in the TCP/IP implementation of Windows 7 and earlier operating systems that enables full blind TCP/IP hijacking attacks. This vulnerability stems from the absence of proper TCP sequence number validation and prediction mechanisms that should be inherent in secure network protocol implementations. The flaw allows attackers to perform idle scans against target systems without direct communication, making it particularly dangerous for network reconnaissance and exploitation activities.
The technical root cause of this vulnerability lies in the predictable nature of TCP sequence number generation within Windows 7 implementations. According to CWE-1230, this weakness falls under the category of "Weakness in Random Number Generation for Cryptographic Protocols" where the operating system fails to implement sufficient entropy in its TCP sequence number generation. The vulnerability specifically affects the TCP/IP stack's ability to maintain secure connection state management, creating opportunities for attackers to inject malicious packets into established connections without being detected.
From an operational perspective, this vulnerability enables attackers to perform sophisticated network reconnaissance through idle scanning techniques that do not require direct interaction with the target system. The attacker can determine which ports are open on a target system by sending TCP packets with specific sequence number patterns that exploit the predictable nature of Windows 7's TCP implementation. This capability directly maps to ATT&CK technique T1046, which involves network service scanning, and T1592, which encompasses reconnaissance through network scanning. The low severity classification by the vendor is misleading given the potential for advanced persistent threats and the wide availability of such scanning techniques.
The impact of this vulnerability extends beyond simple port scanning to include full connection hijacking capabilities that can allow attackers to take control of established TCP sessions. This means that an attacker could potentially intercept and modify data streams, inject malicious content, or redirect traffic through the hijacked connections. The vulnerability affects not only Windows 7 systems but also any implementation that shares the same TCP/IP stack characteristics, including numerous IoT devices that rely on similar protocols. The widespread nature of this issue means that organizations with legacy systems or embedded devices that have not been updated may be exposed to these attacks.
Mitigation strategies for this vulnerability should focus on immediate system updates and network segmentation to prevent unauthorized access to critical systems. Organizations should implement network monitoring solutions that can detect anomalous TCP sequence number patterns and establish proper firewall rules that limit unnecessary network access. The implementation of TCP sequence number randomization techniques and network intrusion detection systems can help detect and prevent exploitation attempts. Additionally, organizations should consider implementing network access controls that limit the exposure of systems to external threats while ensuring that legacy systems are properly isolated from critical network segments. The vulnerability highlights the importance of maintaining up-to-date security patches and implementing proper network security controls to protect against sophisticated attacks that exploit fundamental protocol weaknesses.