CVE-2011-2940 in stunnel
Summary
by MITRE
stunnel 4.40 and 4.41 might allow remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via unspecified vectors.
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Analysis
by VulDB Data Team • 01/11/2025
The vulnerability identified as CVE-2011-2940 affects stunnel versions 4.40 and 4.41, presenting a critical security risk that could enable remote attackers to achieve arbitrary code execution or induce denial of service conditions through heap memory corruption. This issue stems from unspecified vectors within the stunnel application that processes SSL/TLS connections, making it particularly dangerous as it could be exploited across various network environments where stunnel is deployed. The vulnerability specifically targets heap memory management within the application's processing routines, creating potential for memory corruption that could be leveraged by malicious actors to gain unauthorized system access or disrupt service availability.
The technical flaw manifests through improper memory handling mechanisms that fail to adequately validate input data during SSL/TLS connection establishment and data processing. When stunnel receives certain malformed or specially crafted network packets, the application's heap memory allocation and deallocation functions become vulnerable to corruption, potentially allowing attackers to overwrite critical memory locations or execute arbitrary code within the context of the stunnel process. This memory corruption vulnerability aligns with CWE-122, which describes heap-based buffer overflow conditions, and represents a classic example of how improper memory management can create exploitable conditions in network security applications. The vulnerability's impact is amplified by stunnel's widespread deployment as a SSL/TLS proxy and tunneling service across enterprise networks, making it an attractive target for attackers seeking to establish persistent access or disrupt critical services.
The operational impact of this vulnerability extends beyond simple exploitation capabilities to encompass significant business continuity risks and potential data compromise scenarios. Organizations relying on stunnel 4.40 and 4.41 for secure communication channels face potential exposure to remote code execution attacks that could allow attackers to establish backdoors, exfiltrate sensitive data, or pivot to other systems within the network. The heap corruption nature of the vulnerability means that successful exploitation could lead to system crashes, making denial of service a primary concern alongside code execution capabilities. This vulnerability particularly affects environments where stunnel serves as a critical network infrastructure component, including secure email servers, database connections, and other applications requiring encrypted communication channels. The attack surface is broad due to stunnel's role in handling various SSL/TLS protocols and its integration with multiple network services.
Mitigation strategies for CVE-2011-2940 must prioritize immediate version updates to stunnel 4.42 or later releases that contain the necessary patches addressing the heap memory corruption issues. Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected stunnel versions and implement mandatory upgrade procedures across their infrastructure. Network segmentation and access controls should be enforced to limit exposure of stunnel services to trusted networks only, while monitoring systems should be deployed to detect potential exploitation attempts through anomaly detection and log analysis. Security teams should also consider implementing intrusion detection systems that can identify suspicious network traffic patterns associated with known exploitation techniques for heap-based vulnerabilities. The remediation process must include thorough testing of updated stunnel versions in staging environments to ensure compatibility with existing network configurations before deployment to production systems. Additionally, organizations should review their overall security posture and implement regular vulnerability management processes to prevent similar issues from arising in other network security applications. This vulnerability demonstrates the critical importance of maintaining up-to-date security software and following security best practices as outlined in various cybersecurity frameworks including those referenced in the ATT&CK framework for defensive strategies against memory corruption exploits.