CVE-2016-7044 in irssi
Summary
by MITRE
The unformat_24bit_color function in the format parsing code in Irssi before 0.8.20, when compiled with true-color enabled, allows remote attackers to cause a denial of service (heap corruption and crash) via an incomplete 24bit color code.
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Analysis
by VulDB Data Team • 09/19/2022
The vulnerability identified as CVE-2016-7044 represents a critical heap corruption issue affecting the Irssi IRC client software version 0.8.19 and earlier. This flaw exists within the unformat_24bit_color function, which is part of the format parsing code responsible for handling color codes in the client's display output. The vulnerability specifically manifests when Irssi is compiled with true-color support enabled, creating a condition where malformed 24-bit color codes can trigger memory corruption during parsing operations.
The technical implementation of this vulnerability stems from inadequate input validation within the color code parsing mechanism. When Irssi encounters an incomplete 24-bit color code, the unformat_24bit_color function fails to properly handle the malformed data structure, leading to heap corruption. This occurs because the function does not perform sufficient bounds checking or validation before processing color code components, allowing attackers to craft specially formatted color sequences that exploit memory management flaws in the application's heap allocation system. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, though it manifests as heap corruption in this specific implementation.
From an operational perspective, this vulnerability presents a significant denial of service risk to users of Irssi clients. Remote attackers can exploit this flaw by sending IRC messages containing malformed 24-bit color codes to any user running an affected version of Irssi. The exploitation results in immediate application crashes, effectively disrupting communication channels and potentially allowing for persistent service disruption in multi-user environments. The impact extends beyond individual users to entire IRC networks where clients may be running vulnerable versions, as the vulnerability can be triggered through any message containing the malformed color sequence, making it particularly dangerous in public chat environments.
The security implications of CVE-2016-7044 align with ATT&CK technique T1499.004 for network denial of service attacks, where adversaries leverage software vulnerabilities to disrupt service availability. This vulnerability also maps to CWE-787 as an out-of-bounds write condition that can lead to arbitrary code execution if exploited further, though the current manifestation only results in denial of service. The flaw demonstrates poor input sanitization practices and highlights the importance of robust memory management in client-side applications handling user-generated content. Organizations using Irssi should prioritize immediate patching to version 0.8.20 or later, as the vulnerability can be exploited without authentication and requires minimal effort to trigger. System administrators should also implement network-level monitoring to detect potential exploitation attempts and consider disabling true-color support in environments where security is paramount. The vulnerability serves as a reminder of the critical importance of input validation and memory safety practices in client applications that process untrusted data from network sources.