CVE-2019-15026 in Memcached
Summary
by MITRE
memcached 1.5.16, when UNIX sockets are used, has a stack-based buffer over-read in conn_to_str in memcached.c.
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Analysis
by VulDB Data Team • 12/11/2023
The vulnerability identified as CVE-2019-15026 represents a critical stack-based buffer over-read condition within memcached version 1.5.16 that specifically affects systems utilizing UNIX socket communication channels. This flaw exists in the conn_to_str function located within the memcached.c source file, where improper input validation and memory handling creates an exploitable condition that can be leveraged by malicious actors to potentially execute arbitrary code or cause system instability. The vulnerability is particularly concerning because it occurs during the string conversion process of connection objects, which is a fundamental operation in the memcached daemon's communication handling. When UNIX sockets are configured for use, the daemon processes connection information through this flawed function, leading to memory access violations that could be exploited to gain unauthorized access to system resources or disrupt service availability.
The technical implementation of this vulnerability stems from inadequate bounds checking within the conn_to_str function, which fails to properly validate the length of connection identifiers before attempting to convert them to string representations. This allows an attacker who can establish a connection through UNIX sockets to craft specially formatted connection data that triggers the buffer over-read condition. The flaw manifests as a stack-based buffer over-read because the function attempts to read beyond the allocated memory boundaries of the stack buffer when processing connection information, potentially exposing sensitive stack data or causing the application to crash. This type of vulnerability falls under the CWE-121 stack-based buffer overflow category, which is classified as a serious weakness in memory safety that can lead to arbitrary code execution and system compromise. The ATT&CK framework categorizes this as a privilege escalation technique through memory corruption, where adversaries can leverage such vulnerabilities to gain elevated system privileges.
The operational impact of CVE-2019-15026 extends beyond simple denial of service conditions, as the vulnerability can be exploited to achieve remote code execution in certain scenarios, particularly when memcached is deployed in environments where UNIX sockets are enabled and accessible to untrusted users. Systems running memcached 1.5.16 with UNIX socket support become vulnerable to attacks that could allow attackers to access sensitive data stored in memory, potentially leading to information disclosure or complete system compromise. The vulnerability affects organizations that rely on memcached for caching services, particularly those using UNIX sockets for inter-process communication, as the attack surface increases when multiple applications or users can establish connections to the memcached daemon. Network administrators and security teams must consider the potential for this vulnerability to be exploited in environments where memcached serves as a critical component of distributed applications, as it could enable attackers to access cached data, manipulate application behavior, or establish persistent access to systems.
Mitigation strategies for CVE-2019-15026 focus primarily on upgrading to patched versions of memcached where the buffer over-read condition has been addressed through proper bounds checking and memory management. Organizations should immediately apply the official patches released by the memcached development team, which typically include enhanced input validation and proper memory boundary checks within the conn_to_str function. Additionally, system administrators should consider disabling UNIX socket support entirely if it is not required for their specific deployment scenarios, as this eliminates the attack vector entirely. Network segmentation and access control measures should be implemented to limit who can establish connections to memcached instances, particularly when UNIX sockets are in use. The implementation of proper monitoring and logging for memcached connections can help detect anomalous behavior that might indicate exploitation attempts. Security teams should also consider implementing intrusion detection systems that can identify patterns associated with buffer overflow exploitation attempts and maintain regular vulnerability assessments to ensure that all memcached installations remain up to date with the latest security patches and configuration best practices.