CVE-2017-6474 in Wireshark
Summary
by MITRE
In Wireshark 2.2.0 to 2.2.4 and 2.0.0 to 2.0.10, there is a NetScaler file parser infinite loop, triggered by a malformed capture file. This was addressed in wiretap/netscaler.c by validating record sizes.
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Analysis
by VulDB Data Team • 10/15/2019
The vulnerability identified as CVE-2017-6474 represents a critical denial of service flaw in Wireshark versions ranging from 2.2.0 through 2.2.4 and 2.0.0 through 2.0.10. This issue manifests within the NetScaler file parser component, specifically in the wiretap/netscaler.c module, where an infinite loop condition can be triggered by processing malformed capture files. The flaw demonstrates a classic example of inadequate input validation that can be exploited to cause system resource exhaustion and application instability.
The technical implementation of this vulnerability stems from insufficient validation of record sizes within the NetScaler capture file parsing logic. When Wireshark encounters a malformed NetScaler capture file containing invalid or corrupted record size indicators, the parser enters an infinite loop during the processing phase. This occurs because the parsing routine fails to properly validate the size parameters before attempting to iterate through or process the data structures. The vulnerability directly maps to CWE-835, which describes the weakness of a loop with an exit condition that can never be met, resulting in an infinite loop or similar endless iteration.
The operational impact of this vulnerability extends beyond simple application instability, as it can be leveraged by attackers to perform denial of service attacks against systems running vulnerable versions of Wireshark. An attacker who can convince a user to open a maliciously crafted NetScaler capture file can cause the application to consume excessive CPU resources and potentially crash the application entirely. This makes the vulnerability particularly dangerous in environments where Wireshark is used for network analysis and troubleshooting, as users may unknowingly open compromised capture files from untrusted sources.
Network security professionals and analysts using Wireshark for packet analysis and forensic investigations face significant risk from this vulnerability. The attack vector is relatively simple to execute, requiring only the delivery of a malformed capture file to a system running vulnerable Wireshark versions. This vulnerability also aligns with ATT&CK technique T1499.001, which covers network denial of service attacks, as the infinite loop effectively renders the application unavailable for legitimate use. The flaw demonstrates how seemingly benign parsing operations can become security threats when proper input validation is omitted.
The remediation for CVE-2017-6474 was implemented through the addition of proper record size validation within the wiretap/netscaler.c file. This fix ensures that before any processing occurs, the parser validates that record size indicators fall within acceptable ranges and do not contain values that would cause the parsing loop to become infinite. The solution follows established security best practices for input validation and demonstrates the importance of defensive programming techniques in network analysis tools. Users should immediately upgrade to Wireshark versions that include this fix to protect against exploitation, as the vulnerability can be triggered through automated means when processing untrusted network capture files.