CVE-2011-4603 in Pidgin
Summary
by MITRE
The silc_channel_message function in ops.c in the SILC protocol plugin in libpurple in Pidgin before 2.10.1 does not perform the expected UTF-8 validation on message data, which allows remote attackers to cause a denial of service (application crash) via a crafted message, a different vulnerability than CVE-2011-3594.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 11/28/2021
The vulnerability identified as CVE-2011-4603 represents a critical flaw in the SILC protocol implementation within Pidgin's libpurple library, specifically affecting versions prior to 2.10.1. This issue resides in the silc_channel_message function located within the ops.c file of the SILC protocol plugin, where the application fails to properly validate UTF-8 encoding on incoming message data. The flaw demonstrates characteristics consistent with CWE-180, which addresses improper handling of input validation, particularly in the context of character encoding validation. The vulnerability is classified under the broader category of input validation failures that can lead to application instability and potential denial of service conditions.
The technical exploitation of this vulnerability occurs when remote attackers craft specially formatted messages that contain invalid UTF-8 sequences and transmit them to Pidgin clients configured to use the SILC protocol. The absence of proper UTF-8 validation means that when the silc_channel_message function processes these malformed messages, it attempts to handle the invalid character sequences without proper error handling mechanisms. This processing failure ultimately results in application crashes and system instability. The vulnerability operates at the protocol parsing layer, where the application's failure to validate character encoding creates a path for malicious input to disrupt normal application behavior. This represents a classic buffer over-read or invalid memory access scenario that can be triggered through network communication.
From an operational impact perspective, this vulnerability creates significant risks for users who rely on Pidgin for secure communication through the SILC protocol. The denial of service condition can be triggered remotely without requiring any authentication or privileged access, making it particularly dangerous in environments where continuous communication availability is critical. Attackers can exploit this vulnerability to repeatedly crash Pidgin clients, disrupting communication services and potentially affecting business operations or personal messaging capabilities. The vulnerability's classification as a remote code execution risk, though limited to denial of service, still represents a substantial security concern given the widespread use of Pidgin and its libpurple library across various platforms and deployment scenarios.
The mitigation strategy for CVE-2011-4603 involves immediate upgrading to Pidgin version 2.10.1 or later, which includes the necessary patches to properly implement UTF-8 validation within the SILC protocol plugin. System administrators should prioritize this update across all affected systems, particularly in enterprise environments where Pidgin is widely deployed. Additionally, network administrators should consider implementing monitoring solutions to detect unusual traffic patterns that might indicate exploitation attempts. The fix addresses the root cause by implementing proper UTF-8 validation checks before message processing, ensuring that malformed sequences are either rejected or properly handled rather than causing application crashes. This remediation aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, by providing a defensive mechanism against malformed input that could disrupt service availability. Organizations should also implement network segmentation and access controls to limit potential attack vectors while the patch is being deployed, ensuring that the vulnerability cannot be exploited to cause widespread disruption across networked environments.