CVE-2015-8702 in InspIRCd
Summary
by MITRE
The DNS::GetResult function in dns.cpp in InspIRCd before 2.0.19 allows remote DNS servers to cause a denial of service (netsplit) via an invalid character in a PTR response, as demonstrated by a "\032" (whitespace) character in a hostname.
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Analysis
by VulDB Data Team • 11/08/2024
The vulnerability identified as CVE-2015-8702 affects InspIRCd versions prior to 2.0.19 and resides within the DNS::GetResult function in the dns.cpp file. This flaw represents a classic input validation issue that can be exploited to disrupt network services through a denial of service attack. The vulnerability specifically targets the handling of PTR (Pointer) DNS responses, which are used to resolve IP addresses back to hostnames during the IRC connection process. When remote DNS servers provide malformed PTR responses containing invalid characters, particularly the control character "" (whitespace), the vulnerable InspIRCd server becomes susceptible to service disruption.
The technical exploitation of this vulnerability occurs when the DNS resolution process encounters a malformed PTR response that contains characters outside the expected ASCII range for hostnames. The "" character represents a control character that should not appear in valid DNS hostname data, yet the insufficient input validation in the DNS::GetResult function fails to properly sanitize or reject such malformed responses. This processing failure causes the IRC server to mishandle the response, leading to unexpected behavior that can trigger a netsplit within the IRC network. A netsplit occurs when the IRC network becomes partitioned, causing users to lose connectivity between different network segments and effectively disrupting the service for all connected users.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader network stability concerns within IRC communities. When exploited successfully, this vulnerability can cause cascading failures across interconnected IRC networks, as the netsplit effect propagates through the network topology. The vulnerability demonstrates a weakness in the IRC server's error handling and input validation mechanisms, particularly in how it processes external DNS responses that are critical for user authentication and connection establishment. Organizations running InspIRCd servers were vulnerable to this attack vector because the software did not implement proper bounds checking or character validation for DNS response data before processing it for network operations.
The root cause of this vulnerability aligns with CWE-20, which describes improper input validation, and represents a failure to properly sanitize external data sources. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network disruption through manipulation of DNS services, and T1566.002, which involves social engineering via DNS cache poisoning. The vulnerability could be exploited by attackers who gain control of malicious DNS servers or who can manipulate DNS responses through various network interception techniques. Mitigation strategies include upgrading to InspIRCd version 2.0.19 or later, implementing DNS response validation mechanisms, and deploying network monitoring to detect anomalous DNS traffic patterns. Additionally, administrators should consider implementing DNS security extensions and configuring proper input sanitization for all external data processing to prevent similar vulnerabilities in other network services.