CVE-2015-8720 in Wireshark
Summary
by MITRE
The dissect_ber_GeneralizedTime function in epan/dissectors/packet-ber.c in the BER dissector in Wireshark 1.12.x before 1.12.9 and 2.0.x before 2.0.1 improperly checks an sscanf return value, which allows remote attackers to cause a denial of service (application crash) via a crafted packet.
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Analysis
by VulDB Data Team • 07/02/2022
The vulnerability identified as CVE-2015-8720 represents a critical denial of service flaw within Wireshark's Basic Encoding Rules (BER) dissector component. This issue affects Wireshark versions 1.12.x prior to 1.12.9 and 2.0.x prior to 2.0.1, where the dissect_ber_GeneralizedTime function fails to properly validate the return value from sscanf operations. The flaw exists in the epan/dissectors/packet-ber.c file, which is responsible for parsing BER-encoded data structures commonly used in telecommunications and network protocols. The improper handling of sscanf return values creates a condition where malformed input can trigger unexpected behavior in the application's memory management and execution flow.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a specially formatted packet containing malformed GeneralizedTime data within BER-encoded structures. When Wireshark processes such packets, the dissect_ber_GeneralizedTime function attempts to parse the time data using sscanf but does not verify whether the parsing operation successfully extracted the expected number of fields. This oversight allows attackers to manipulate the parsing logic through crafted input, potentially leading to buffer overflows, null pointer dereferences, or other memory corruption conditions that ultimately result in application crashes. The vulnerability stems from a classic CWE-248 issue where an exception or error condition is not properly handled, combined with CWE-121 buffer overflow patterns that can occur when parsing untrusted input data.
The operational impact of CVE-2015-8720 extends beyond simple service disruption, as it can be leveraged in various attack scenarios within network monitoring and forensic analysis environments. Network administrators and security analysts who rely on Wireshark for packet analysis and troubleshooting become vulnerable to remote exploitation, potentially allowing attackers to disrupt network monitoring operations or cause denial of service against systems that depend on Wireshark for protocol analysis. The vulnerability is particularly concerning in environments where Wireshark is used for continuous network monitoring or in security operations centers where automated packet capture and analysis systems may be targeted. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 (Endpoint Denial of Service) and T1566.001 (Phishing with Malicious Attachment), as it enables remote attackers to cause system instability through crafted network traffic.
Mitigation strategies for CVE-2015-8720 primarily involve immediate version upgrades to Wireshark 1.12.9 or 2.0.1 and later releases where the sscanf return value checking has been properly implemented. Network administrators should also consider implementing network segmentation and access controls to limit exposure to potentially malicious traffic, while monitoring for unusual packet patterns that might indicate exploitation attempts. Additionally, organizations should maintain updated network security monitoring tools and ensure that all network analysis equipment is regularly patched and updated to prevent exploitation of known vulnerabilities. The fix implemented in affected versions addresses the core issue by ensuring that sscanf return values are properly validated before proceeding with subsequent operations, thereby preventing the execution path that leads to application crashes. This vulnerability highlights the importance of proper input validation and error handling in network protocol analysis tools, where the processing of untrusted data can lead to system instability and potential security implications.