CVE-2011-3594 in libpurple
Summary
by MITRE
The g_markup_escape_text function in the SILC protocol plug-in in libpurple 2.10.0 and earlier, as used in Pidgin and possibly other products, allows remote attackers to cause a denial of service (crash) via invalid UTF-8 sequences that trigger use of invalid pointers and an out-of-bounds read, related to interactions with certain versions of glib2.
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Analysis
by VulDB Data Team • 11/26/2021
The vulnerability identified as CVE-2011-3594 represents a critical memory corruption issue within the SILC protocol plugin of libpurple version 2.10.0 and earlier. This flaw specifically affects the g_markup_escape_text function which is responsible for handling markup text processing in the SILC protocol implementation. The vulnerability manifests when the function encounters invalid UTF-8 sequences during text processing, creating a scenario where the application attempts to access invalid memory pointers and execute out-of-bounds read operations. The root cause stems from inadequate input validation within the text processing pipeline, particularly when dealing with malformed UTF-8 data that the function was not designed to handle gracefully.
This vulnerability operates at the intersection of memory safety and character encoding validation, creating a path for remote attackers to exploit the application's text processing capabilities. The flaw is particularly dangerous because it can be triggered through normal communication channels when the affected application receives malformed text data from remote peers. The use of invalid pointers and out-of-bounds memory access patterns directly violates fundamental memory safety principles and can lead to application crashes or potentially more severe exploitation scenarios. The vulnerability is classified under CWE-125 as an out-of-bounds read and CWE-787 as an out-of-bounds write, representing multiple memory safety issues that can compromise system stability. The interaction with glib2 versions creates a complex exploitation vector where the underlying library's handling of character encoding conflicts with the plugin's text processing logic.
The operational impact of this vulnerability extends beyond simple denial of service, as it can severely disrupt communication services within applications that rely on libpurple for instant messaging functionality. When exploited, the vulnerability causes applications like Pidgin to crash, effectively terminating user sessions and disrupting ongoing communications. This makes the vulnerability particularly dangerous in environments where continuous communication is critical, such as business collaboration platforms or emergency response systems. The remote nature of the attack means that malicious actors can trigger the vulnerability without requiring physical access to the target system, making it a significant threat to networked applications. The vulnerability affects not just Pidgin but potentially other applications that utilize the same libpurple library, creating a widespread impact across multiple software products that implement the SILC protocol.
Mitigation strategies for this vulnerability focus on immediate patching of the affected libpurple library to version 2.10.1 or later, which includes proper input validation and memory safety improvements. System administrators should prioritize updating all affected applications that utilize the vulnerable library, particularly those in environments with high communication traffic. Implementing additional input sanitization at the application level can provide defense-in-depth measures, though the primary solution remains the official library patch. Network-level protections such as monitoring for malformed UTF-8 sequences in communication traffic can help detect potential exploitation attempts, while application firewalls can be configured to filter suspicious text data. The vulnerability demonstrates the importance of proper character encoding validation in security-critical applications and aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as the exploitation relies on text processing vulnerabilities that could potentially be leveraged for more advanced attacks if combined with other exploitation techniques. Organizations should also implement regular security assessments of their messaging and communication platforms to identify similar vulnerabilities in other protocol implementations.