CVE-2012-3291 in OpenConnect
Summary
by MITRE
Heap-based buffer overflow in OpenConnect 3.18 allows remote servers to cause a denial of service via a crafted greeting banner.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability CVE-2012-3291 represents a heap-based buffer overflow in OpenConnect version 3.18 that specifically targets the client software used for establishing secure VPN connections. This issue arises from inadequate input validation when processing greeting banners from remote servers, creating a condition where maliciously crafted server responses can trigger memory corruption. The vulnerability is classified under CWE-121 Heap-based Buffer Overflow, which falls within the broader category of memory safety issues that have historically been a primary attack vector in cybersecurity exploits. OpenConnect is widely used for connecting to Cisco AnyConnect VPN services, making this vulnerability particularly concerning for enterprise environments that rely on secure remote access solutions.
The technical flaw manifests when the OpenConnect client receives a greeting banner from a remote server during the initial connection handshake process. The client fails to properly validate the length of the banner data before copying it into a heap-allocated buffer, allowing an attacker to exceed the buffer boundaries and overwrite adjacent memory locations. This heap corruption can result in unpredictable behavior including application crashes, memory corruption, or potentially more severe consequences if the overflow allows for code execution. The vulnerability specifically affects the client-side processing of server responses, meaning that an attacker would need to control or compromise a VPN server to exploit this weakness. The attack requires no authentication from the victim and can be executed remotely, making it particularly dangerous in scenarios where users connect to untrusted VPN servers.
The operational impact of CVE-2012-3291 extends beyond simple denial of service conditions, as heap corruption can lead to system instability and potential information disclosure. When the buffer overflow occurs, it typically results in an application crash that prevents legitimate users from establishing VPN connections to affected servers. Organizations using OpenConnect for remote access may experience service disruption and increased support overhead as users encounter connection failures. The vulnerability is particularly concerning for organizations with mobile workforces that depend on secure VPN connectivity, as it could be exploited to disrupt critical business operations. Additionally, the nature of heap-based overflows means that the effects can be inconsistent and difficult to predict, making detection and remediation more challenging for security teams. This vulnerability aligns with ATT&CK technique T1210 Exploitation of Remote Services, specifically targeting client-side applications that establish network connections to remote servers.
Mitigation strategies for CVE-2012-3291 should focus on immediate patching of affected OpenConnect installations, as version 3.19 and later contain fixes for this vulnerability. Organizations should implement network segmentation to limit exposure to untrusted VPN servers and consider deploying additional security monitoring to detect abnormal connection behavior. The vulnerability demonstrates the importance of input validation in network protocols and highlights the need for robust buffer management practices in client applications. Security teams should also consider implementing network access controls that prevent unauthorized VPN server configurations and maintain updated inventories of all VPN clients and servers within their environments. Organizations with legacy systems running vulnerable versions of OpenConnect should prioritize upgrading to patched versions while maintaining proper change management processes to ensure secure deployment of updates across their infrastructure.