CVE-2009-3085 in Pidgin
Summary
by MITRE
The XMPP protocol plugin in libpurple in Pidgin before 2.6.2 does not properly handle an error IQ stanza during an attempted fetch of a custom smiley, which allows remote attackers to cause a denial of service (application crash) via XHTML-IM content with cid: images.
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Analysis
by VulDB Data Team • 08/22/2021
The vulnerability identified as CVE-2009-3085 affects the XMPP protocol implementation within libpurple, the core library that powers the Pidgin instant messaging client. This flaw exists in versions prior to 2.6.2 and represents a significant security weakness that could be exploited to disrupt service availability. The issue specifically manifests when the client attempts to process XHTML-IM content containing cid: images during a custom smiley fetch operation, creating a scenario where maliciously crafted messages can trigger unexpected behavior in the application's handling of error IQ stanzas.
The technical root cause of this vulnerability lies in the improper error handling mechanism within the XMPP plugin's processing of IQ (Info/Query) stanzas. When Pidgin encounters an error condition while attempting to retrieve custom smileys through XHTML-IM formatted content, the application fails to properly validate or sanitize the incoming error IQ stanza. This inadequate error handling leads to a memory corruption condition that ultimately results in an application crash. The vulnerability is particularly concerning because it operates at the protocol level, meaning that an attacker can exploit this weakness simply by sending a specially crafted message to a victim using an affected version of Pidgin.
From an operational perspective, this vulnerability creates a reliable denial of service condition that can be exploited by remote attackers without requiring any special privileges or authentication. The attack vector is straightforward: an attacker sends a malicious message containing XHTML-IM content with cid: references to a user running an affected Pidgin version. The application's failure to properly handle the error response during the smiley fetch process causes an uncontrolled crash, forcing the user to restart the application and potentially lose unsaved chat conversations. This makes the vulnerability particularly dangerous in environments where continuous communication is critical.
The impact of this vulnerability aligns with CWE-20, which describes improper input validation, and demonstrates how inadequate error handling can lead to system instability. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service, as it enables an attacker to disrupt service availability through crafted network traffic. The vulnerability also relates to T1566.001, representing a phishing attack vector where malicious content could be embedded within seemingly legitimate chat messages. The lack of proper bounds checking and error validation in the XMPP plugin creates a predictable crash scenario that can be reliably reproduced, making it an attractive target for attackers seeking to disrupt communications.
Mitigation strategies for this vulnerability include immediate upgrading to Pidgin version 2.6.2 or later, which contains the necessary patches to properly handle error IQ stanzas during smiley fetch operations. Network administrators should also implement message filtering mechanisms that can detect and block XHTML-IM content containing cid: references, though this approach may impact legitimate functionality. Additionally, users should be educated about the risks of accepting messages from untrusted sources, as the vulnerability can be exploited through social engineering tactics. The fix implemented in the patched version addresses the core issue by ensuring proper validation of error conditions and implementing robust error handling procedures that prevent memory corruption during the processing of malformed XMPP stanzas.