CVE-2018-7329 in Wireshark
Summary
by MITRE
In Wireshark 2.4.0 to 2.4.4 and 2.2.0 to 2.2.12, epan/dissectors/packet-s7comm.c had an infinite loop that was addressed by correcting off-by-one errors.
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Analysis
by VulDB Data Team • 02/10/2023
The vulnerability identified as CVE-2018-7329 represents a critical flaw in Wireshark's S7 communication protocol dissector that could lead to denial of service conditions. This issue affected multiple versions of Wireshark including the 2.4.0 through 2.4.4 release series and the 2.2.0 through 2.2.12 release series, making it a widespread concern across a significant portion of the software's user base. The flaw specifically resided within the epan/dissectors/packet-s7comm.c file which is responsible for dissecting Siemens S7 communication protocol packets used in industrial control systems and manufacturing environments. The S7 protocol is widely deployed in supervisory control and data acquisition systems, making this vulnerability particularly concerning for operational technology environments.
The technical root cause of this vulnerability stems from an off-by-one error that created an infinite loop condition within the dissector's packet parsing logic. When processing specially crafted S7 protocol packets, the dissector would enter a loop where the loop counter variable was not properly incremented or decremented, causing the loop to continue indefinitely. This type of flaw falls under CWE-121, which describes stack-based buffer overflow conditions, though in this specific case the manifestation was an infinite loop rather than a buffer overflow. The off-by-one error typically occurs when programmers incorrectly handle loop boundary conditions, leading to scenarios where loop termination conditions are never met. This particular implementation error demonstrates a failure in proper loop control structure management and boundary condition validation.
The operational impact of this vulnerability extends beyond simple denial of service as it could potentially disrupt critical network monitoring and analysis operations in industrial environments. When an infinite loop occurs in a network protocol dissector, it causes the entire Wireshark application to become unresponsive or consume excessive CPU resources, effectively making it impossible for network administrators to analyze traffic or diagnose network issues. In industrial control systems where Wireshark is commonly used for troubleshooting and security analysis, this vulnerability could create significant operational disruptions. The S7 protocol is fundamental to many industrial automation systems, so any disruption to tools analyzing this traffic could affect production monitoring and security operations. This vulnerability aligns with ATT&CK technique T1499.001, which covers network denial of service attacks, though in this case the attack vector is through malformed protocol data rather than external network flooding.
The remediation for this vulnerability involved correcting the off-by-one errors in the packet-s7comm.c file by ensuring proper loop boundary conditions and counter management. This fix required careful analysis of the dissector's parsing logic and modification of the loop control structures to prevent the infinite execution path. The resolution demonstrates the importance of thorough code review processes and boundary condition validation in protocol dissector development. Security researchers and developers should ensure that loop structures in network protocol parsing code are carefully validated to prevent similar issues, particularly when handling variable-length protocol data. The fix for CVE-2018-7329 required attention to both the loop termination conditions and the increment/decrement operations that control loop progression, ensuring that all code paths properly advance loop counters to prevent indefinite execution. This vulnerability serves as a reminder of the critical importance of proper loop management in network analysis tools, where malformed data could potentially be exploited to cause system instability or resource exhaustion.