CVE-2018-5206 in irssi
Summary
by MITRE
When the channel topic is set without specifying a sender, Irssi before 1.0.6 may dereference a NULL pointer.
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Analysis
by VulDB Data Team • 12/20/2019
The vulnerability identified as CVE-2018-5206 resides within the Irssi IRC client software, specifically affecting versions prior to 1.0.6. This issue manifests when processing channel topic changes that occur without an explicit sender specification, creating a scenario where the application attempts to access memory through a null pointer reference. The flaw represents a classic null pointer dereference vulnerability that can lead to application instability and potential exploitation. Irssi, being a widely-used terminal-based IRC client, processes numerous network events including channel topic updates, making this vulnerability particularly concerning for users who rely on the software for communication.
The technical root cause of this vulnerability stems from improper input validation within the channel topic handling mechanism. When a channel topic is updated through the IRC protocol, the system should verify that all necessary components are present before attempting to process the information. In the affected versions, when no sender is specified for a topic change, the application fails to validate whether the sender pointer is null before attempting to dereference it. This memory access violation occurs in the context of message processing where the application assumes that all expected fields will be populated, leading to a crash when the assumption proves incorrect. The vulnerability specifically impacts the channel topic functionality and occurs during the parsing and handling of topic update messages received from IRC servers.
The operational impact of CVE-2018-5206 extends beyond simple application crashes, potentially creating denial of service conditions for users relying on Irssi for their IRC communications. An attacker could exploit this vulnerability by crafting malicious topic update messages that omit sender information, causing the client to crash whenever it attempts to process such messages. This type of vulnerability aligns with CWE-476, which describes NULL Pointer Dereference, and represents a common class of memory safety issues that can be leveraged for service disruption. The vulnerability affects the availability aspect of the system's security posture, as legitimate users may experience interruptions in their IRC sessions due to unexpected application termination.
Mitigation strategies for CVE-2018-5206 primarily involve upgrading to Irssi version 1.0.6 or later, where the null pointer dereference has been addressed through proper input validation. System administrators and users should prioritize updating their Irssi installations to prevent exploitation. Additionally, network administrators can implement monitoring solutions to detect unusual topic update patterns that might indicate attempts to exploit this vulnerability. The fix implemented in version 1.0.6 demonstrates proper defensive programming practices that include null pointer checks before memory access operations, aligning with secure coding guidelines and best practices. Organizations should also consider implementing network segmentation and access controls to limit exposure to potentially malicious IRC traffic that could be used to exploit this and similar vulnerabilities. This vulnerability highlights the importance of thorough input validation and memory safety practices in network communication applications, particularly those handling real-time data streams from potentially untrusted sources.