CVE-2017-5196 in irssi
Summary
by MITRE
Irssi 0.8.18 before 0.8.21 allows remote attackers to cause a denial of service (out-of-bounds read and crash) via vectors involving strings that are not UTF8.
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Analysis
by VulDB Data Team • 09/03/2020
The vulnerability identified as CVE-2017-5196 affects Irssi version 0.8.18 and earlier versions before 0.8.21, representing a critical out-of-bounds read flaw that can be exploited remotely to cause denial of service conditions. This vulnerability specifically targets the application's handling of string data that does not conform to UTF-8 encoding standards, creating a scenario where maliciously crafted input can trigger memory access violations.
The technical flaw manifests in Irssi's string processing routines where the application fails to properly validate or sanitize input strings that are not encoded in UTF-8 format. When such malformed strings are processed, the software attempts to access memory locations beyond the bounds of allocated buffers, leading to unpredictable behavior including application crashes and system instability. This type of vulnerability falls under CWE-129, which addresses improper validation of array indices, and more specifically aligns with CWE-787, which covers out-of-bounds write operations that can result in memory corruption.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by remote attackers to systematically destabilize Irssi-based chat servers and client applications. Attackers can craft malicious messages or data streams containing non-UTF8 strings that, when processed by the vulnerable software, will trigger the out-of-bounds read condition and subsequently cause the application to crash. This creates a reliable method for conducting denial of service attacks against systems running affected versions of Irssi, potentially affecting communication channels and user access to chat services.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through application-level exploitation. The attack vector requires minimal sophistication and can be automated, making it particularly dangerous in environments where Irssi is used for critical communications. The vulnerability demonstrates a fundamental weakness in input validation and memory management practices within the application's string handling code.
The recommended mitigation strategy involves immediate upgrading to Irssi version 0.8.21 or later, which contains the necessary patches to address the out-of-bounds read vulnerability. Organizations should also implement additional defensive measures such as input sanitization at network boundaries, monitoring for unusual crash patterns, and maintaining up-to-date security patches across all systems utilizing Irssi. Network administrators should consider implementing rate limiting and input validation rules to prevent exploitation attempts while awaiting the deployment of official patches. The vulnerability serves as a reminder of the importance of proper input validation and memory safety practices in network applications, particularly those handling user-generated content and real-time communication data.