CVE-2016-2377 in Pidgin
Summary
by MITRE
A buffer overflow vulnerability exists in the handling of the MXIT protocol in Pidgin. Specially crafted MXIT data sent by the server could potentially result in an out-of-bounds write of one byte. A malicious server can send a negative content-length in response to a HTTP request triggering the vulnerability.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 04/20/2025
The CVE-2016-2377 vulnerability represents a critical buffer overflow flaw in Pidgin's MXIT protocol implementation that exposes users to potential remote code execution risks. This vulnerability specifically targets the handling of malformed MXIT data packets that can be transmitted through the Instant Messaging protocol, where the client processes incoming data without proper bounds checking mechanisms. The MXIT protocol is used for communication with the MXit messaging service, which was popular in South Africa and other regions, making this vulnerability particularly concerning for users of this messaging platform. The vulnerability stems from insufficient input validation during the parsing of HTTP responses that contain negative content-length headers, which should never occur in legitimate network communications but can be exploited by malicious actors.
The technical exploitation of this vulnerability occurs when a malicious MXit server sends specially crafted HTTP responses containing negative content-length values that trigger improper memory management within Pidgin's protocol handler. This condition causes the application to perform an out-of-bounds write operation of exactly one byte, which can potentially overwrite adjacent memory locations and corrupt the application's execution flow. The flaw is classified as a buffer overflow under CWE-121, which specifically addresses stack-based buffer overflow conditions where insufficient bounds checking allows attackers to write beyond allocated memory boundaries. The vulnerability is particularly dangerous because it requires no user interaction beyond connecting to a malicious server, making it a passive attack vector that can compromise systems without user awareness.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to include potential remote code execution capabilities that could allow attackers to gain unauthorized access to affected systems. When exploited successfully, the one-byte out-of-bounds write can be leveraged to manipulate program execution flow, potentially leading to arbitrary code execution with the privileges of the affected user. This vulnerability affects all versions of Pidgin that support MXIT protocol handling, making it a widespread concern for users of the messaging client. The attack vector is particularly concerning because it can be executed through legitimate network communication channels, requiring only that the victim connects to a malicious MXit server that responds with crafted HTTP headers containing negative content-length values.
Mitigation strategies for CVE-2016-2377 focus on immediate patching of affected Pidgin versions and implementation of network-level protections to prevent access to malicious MXit servers. The most effective solution involves updating to Pidgin versions that include proper bounds checking and input validation for MXIT protocol data handling, which addresses the underlying CWE-121 buffer overflow condition. Network administrators should implement filtering mechanisms to block negative content-length headers in HTTP responses and consider disabling MXIT protocol support entirely if the service is not required. From an ATT&CK framework perspective, this vulnerability maps to T1203 - Exploitation for Client Execution and T1059 - Command and Scripting Interpreter, as attackers can leverage the buffer overflow to execute arbitrary code on victim systems. Organizations should also implement monitoring for unusual HTTP response patterns and establish secure configuration policies that prevent automatic connection to untrusted messaging servers. The vulnerability demonstrates the importance of proper input validation and memory management practices in client-side applications, particularly those handling network protocols that may encounter malformed data from untrusted sources.