CVE-2017-15227 in irssi
Summary
by MITRE
Irssi before 1.0.5, while waiting for the channel synchronisation, may incorrectly fail to remove destroyed channels from the query list, resulting in use-after-free conditions when updating the state later on.
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Analysis
by VulDB Data Team • 01/04/2023
The vulnerability identified as CVE-2017-15227 represents a critical memory safety issue within the Irssi IRC client software version 1.0.4 and earlier. This flaw manifests during the channel synchronization process when the application fails to properly clean up destroyed channel references from its internal query list structure. The root cause lies in the improper handling of channel lifecycle management, specifically in scenarios where channels are rapidly created and destroyed during network synchronization events. This memory management deficiency creates a use-after-free condition that can be exploited by malicious actors to execute arbitrary code or cause application instability.
The technical implementation of this vulnerability stems from a race condition and memory cleanup inconsistency within Irssi's channel management subsystem. When the client processes channel synchronization requests, it maintains an internal data structure containing references to active and recently destroyed channels. The flaw occurs when the application incorrectly retains references to channels that have already been destroyed, leading to memory locations that are freed but still accessed during subsequent state updates. This use-after-free condition falls under the CWE-416 vulnerability category, specifically addressing improper cleanup of dynamically allocated memory resources. The vulnerability is particularly dangerous because it can be triggered during normal IRC network operations when users join and leave channels rapidly, making it exploitable in real-world scenarios.
The operational impact of this vulnerability extends beyond simple application crashes to potentially enable remote code execution capabilities. Attackers can craft specially crafted IRC messages or network conditions that force the client into the problematic code path where destroyed channels remain in the query list. When the application later attempts to update the state of these freed memory locations, it can result in memory corruption that allows for arbitrary code execution with the privileges of the affected user. This makes the vulnerability particularly concerning for users who frequently connect to public IRC networks or participate in multi-user chat environments where malicious actors could easily exploit the flaw. The attack surface is broad as the vulnerability can be triggered through standard IRC protocol operations without requiring special privileges or authentication.
Mitigation strategies for CVE-2017-15227 focus primarily on immediate software updates to version 1.0.5 or later, which contains the necessary patches to properly handle channel cleanup during synchronization events. System administrators should implement comprehensive patch management protocols to ensure all affected installations are updated promptly. Network monitoring solutions should be configured to detect unusual IRC client behavior that might indicate exploitation attempts. The fix addresses the core issue by implementing proper reference counting and memory cleanup routines that ensure destroyed channels are completely removed from the query list before any state update operations occur. Organizations should also consider implementing application sandboxing and privilege separation measures to limit the potential impact if exploitation were to occur. Additionally, users should be educated about the risks of connecting to untrusted IRC networks and the importance of keeping client software updated to prevent exploitation of known vulnerabilities.