CVE-2017-7700 in Wireshark
Summary
by MITRE
In Wireshark 2.2.0 to 2.2.5 and 2.0.0 to 2.0.11, the NetScaler file parser could go into an infinite loop, triggered by a malformed capture file. This was addressed in wiretap/netscaler.c by ensuring a nonzero record size.
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Analysis
by VulDB Data Team • 11/29/2022
The vulnerability identified as CVE-2017-7700 represents a critical denial of service flaw within Wireshark's network protocol analysis capabilities. This issue affects specific versions of Wireshark including releases 2.2.0 through 2.2.5 and 2.0.0 through 2.0.11, where the NetScaler file parser component exhibits problematic behavior when processing malformed capture files. The flaw manifests as an infinite loop condition that can be triggered by specially crafted input data, potentially leading to system resource exhaustion and complete application unresponsiveness. The vulnerability resides in the wiretap/netscaler.c file, which handles the parsing of NetScaler-specific capture files used for network traffic analysis and troubleshooting.
The technical root cause of this vulnerability stems from inadequate input validation within the NetScaler file parser implementation. When Wireshark encounters a malformed capture file containing malformed record structures, the parser fails to properly validate record sizes before processing subsequent data segments. This lack of proper boundary checking allows the parsing logic to enter an infinite loop where it repeatedly processes the same invalid data structure without proper termination conditions. The flaw specifically occurs when the parser attempts to read records with zero or invalid sizes, causing the processing loop to continue indefinitely until system resources are exhausted. This type of vulnerability falls under CWE-835, which addresses infinite loops in software implementations, and represents a classic example of improper input validation leading to resource exhaustion.
The operational impact of CVE-2017-7700 extends beyond simple application instability, as it can be exploited by attackers to perform denial of service attacks against systems running vulnerable versions of Wireshark. Network security analysts and engineers who rely on Wireshark for traffic analysis and incident response may find their investigative capabilities compromised when processing maliciously crafted capture files. The infinite loop condition can cause complete system hangs, requiring manual intervention to terminate the application process and potentially leading to extended downtime during critical security investigations. This vulnerability particularly affects organizations that process third-party network captures or receive untrusted traffic data, as any interaction with a malformed NetScaler file could trigger the exploitable condition. The attack surface is significant within network security operations where analysts frequently handle diverse capture files from various sources.
Mitigation strategies for CVE-2017-7700 focus on immediate version updates to patched releases of Wireshark where the vulnerability has been resolved through proper input validation. The fix implemented in wiretap/netscaler.c ensures that record sizes are validated to be nonzero before processing, preventing the infinite loop condition from occurring. Network security teams should prioritize updating to Wireshark versions that include the patch, typically those released after the vulnerability disclosure. Additionally, organizations can implement defensive measures such as validating capture file integrity before processing, using automated tools to scan for malformed files, and establishing network segmentation to limit exposure to potentially malicious capture data. The vulnerability demonstrates the importance of robust input validation in protocol parsers and aligns with ATT&CK technique T1499.001, which covers network denial of service attacks through resource exhaustion, highlighting the need for proper boundary checking in network analysis tools.