CVE-2015-2778 in Quassel
Summary
by MITRE
Quassel before 0.12-rc1 uses an incorrect data-type size when splitting a message, which allows remote attackers to cause a denial of service (crash) via a long CTCP query containing only multibyte characters.
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Analysis
by VulDB Data Team • 05/03/2022
The vulnerability described in CVE-2015-2778 affects Quassel, an open-source IRC client that provides a persistent chat experience across multiple devices. This issue manifests in versions prior to 0.12-rc1 where the application fails to properly handle data type sizing during message splitting operations. The flaw specifically occurs when processing CTCP queries that contain exclusively multibyte characters, creating a condition that leads to application instability and potential system crashes.
The technical root cause of this vulnerability stems from improper handling of character encoding within the message processing pipeline. When Quassel encounters a CTCP query containing only multibyte characters such as those found in unicode or utf-8 encoded text, the application incorrectly calculates the data type size during message splitting operations. This miscalculation results in buffer overflows or memory corruption scenarios that cause the application to terminate unexpectedly. The vulnerability is classified under CWE-129 as an improper validation of array index, specifically manifesting as an out-of-bounds read or write condition. The flaw represents a classic buffer manipulation error where the application fails to properly validate the boundaries of data structures during processing.
From an operational perspective, this vulnerability presents a significant denial of service threat to Quassel users and administrators. Remote attackers can exploit this weakness by sending specially crafted CTCP queries containing only multibyte characters to any Quassel client or server instance. The attack requires minimal privileges and can be executed from any network location, making it particularly dangerous in public or shared network environments. The impact extends beyond simple service disruption as the application crash can result in loss of ongoing chat sessions, potential data corruption, and interruption of critical communication channels for users relying on Quassel for their IRC communications.
The security implications of CVE-2015-2778 align with ATT&CK technique T1499.004 which covers network denial of service attacks. The vulnerability can be leveraged as part of a broader attack chain where an adversary seeks to disrupt communication services and potentially gain access to sensitive information transmitted through the compromised IRC infrastructure. Organizations using Quassel should consider this vulnerability as a potential entry point for more sophisticated attacks, particularly in environments where IRC communication serves as a critical communication channel. The flaw also demonstrates poor input validation practices that could be exploited in conjunction with other vulnerabilities to escalate privileges or achieve persistent access to affected systems.
Mitigation strategies for CVE-2015-2778 should prioritize immediate patching of affected Quassel installations to version 0.12-rc1 or later, which contains the necessary fixes for proper data type size handling during message splitting operations. Network administrators should implement monitoring solutions to detect unusual CTCP query patterns and consider implementing rate limiting or message size restrictions for incoming IRC traffic. Additionally, organizations should conduct thorough vulnerability assessments to identify any other applications or systems using similar data type handling mechanisms that might be susceptible to analogous buffer manipulation attacks. The fix implemented in the patched versions addresses the core issue by ensuring proper validation of character encoding boundaries and implementing robust error handling for multibyte character sequences during message processing operations.