CVE-2017-9468 in irssi
Summary
by MITRE
In Irssi before 1.0.3, when receiving a DCC message without source nick/host, it attempts to dereference a NULL pointer. Thus, remote IRC servers can cause a crash.
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Analysis
by VulDB Data Team • 12/26/2020
The vulnerability identified as CVE-2017-9468 represents a critical null pointer dereference flaw in Irssi version 1.0.2 and earlier, affecting the popular IRC client software. This issue stems from inadequate input validation within the DCC (Direct Client-to-Client) messaging system, which is commonly used for file transfers and private communications between IRC clients. The vulnerability specifically manifests when Irssi receives a DCC message that lacks proper source identification information including the nicknames or host details typically associated with such communications. This scenario creates a condition where the software attempts to access memory locations through a null pointer reference, leading to an immediate crash of the application.
From a technical perspective, this vulnerability maps directly to CWE-476, which describes the weakness of null pointer dereference in software systems. The flaw occurs at the application level within Irssi's DCC message processing subsystem, where the code assumes the presence of valid source identification data without proper validation checks. When remote IRC servers send malformed DCC messages lacking the expected header information, the application's internal state becomes corrupted, causing the program to terminate unexpectedly. This behavior represents a classic denial-of-service condition that can be exploited by malicious actors to disrupt IRC communications and potentially impact network availability for legitimate users.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged in coordinated attacks against IRC networks where multiple clients are simultaneously targeted. The remote exploitation nature means that attackers do not require local access to the system, making this a particularly dangerous vulnerability for network administrators managing IRC infrastructure. The crash condition affects the entire Irssi application, potentially causing users to lose their connection to IRC servers and disrupting ongoing conversations or file transfer operations. This vulnerability also highlights the importance of proper error handling in network protocols, as the application fails to gracefully handle malformed input rather than attempting to recover or log the incident.
Mitigation strategies for this vulnerability involve upgrading to Irssi version 1.0.3 or later, which contains the necessary patches to properly validate DCC message headers and prevent null pointer dereference conditions. System administrators should also implement network monitoring to detect unusual DCC message patterns that might indicate attempted exploitation. The fix addresses the underlying CWE-476 weakness by introducing proper null checks before pointer dereference operations, ensuring that the application can handle malformed input gracefully without crashing. Additionally, organizations using Irssi should consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities in their IRC environments. This vulnerability demonstrates the critical importance of input validation and error handling in network applications, aligning with ATT&CK technique T1499 for network disruption through application-level attacks. The remediation process should include comprehensive testing of the patched version to ensure that legitimate DCC functionality remains intact while preventing the exploitation vector that leads to application crashes.