CVE-2011-2678 in VPN Client
Summary
by MITRE
The Cisco VPN Client 5.0.7.0240 and 5.0.7.0290 on 64-bit Windows platforms uses weak permissions (NT AUTHORITY\INTERACTIVE:F) for cvpnd.exe, which allows local users to gain privileges by replacing this executable file with an arbitrary program, aka Bug ID CSCtn50645. NOTE: this vulnerability exists because of a CVE-2007-4415 regression.
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Analysis
by VulDB Data Team • 01/12/2018
The vulnerability identified as CVE-2011-2678 represents a critical privilege escalation flaw within Cisco VPN Client versions 5.0.7.0240 and 5.0.7.0290 running on 64-bit Windows systems. This issue stems from improper file permissions assigned to the cvpnd.exe executable component, which serves as a core element of the VPN client's operation. The affected executable is configured with weak permissions that grant broad access rights to the NT AUTHORITY\INTERACTIVE user group, specifically with full file system permissions (F). This configuration creates a significant security gap that adversaries can exploit to elevate their privileges from standard user level to system level access. The vulnerability specifically manifests when local users can manipulate the cvpnd.exe file due to these overly permissive access controls, allowing them to substitute it with malicious code that will execute with elevated privileges.
The technical exploitation of this vulnerability follows a straightforward yet dangerous methodology that aligns with common privilege escalation attack patterns documented in the ATT&CK framework under privilege escalation techniques. Attackers can simply replace the legitimate cvpnd.exe file with a malicious executable that maintains the same name and location, ensuring that when the VPN client service attempts to execute this component, it inadvertently runs the attacker-controlled code. This type of attack leverages the principle of least privilege violation, where system components are granted more access rights than necessary. The vulnerability directly correlates to CWE-276, which addresses incorrect permissions for critical resources, and demonstrates how improper access control configurations can lead to severe security consequences. The regression aspect of this vulnerability, as noted in the description, indicates that this was a previously identified issue (CVE-2007-4415) that was reintroduced or not properly addressed in the newer client versions, highlighting the importance of thorough regression testing in security patches.
The operational impact of CVE-2011-2678 extends beyond simple privilege escalation, as successful exploitation can provide attackers with complete system control and access to all data and resources available to the compromised system. This vulnerability affects organizations that deploy Cisco VPN clients, particularly those with 64-bit Windows environments where the vulnerable versions are installed. The implications are especially concerning for enterprises that rely on VPN connectivity for remote access, as local users with minimal privileges could potentially gain administrative access to corporate networks. The vulnerability can be exploited by any local user, making it particularly dangerous in shared or multi-user environments where users may not be fully trusted. Organizations using these vulnerable versions face significant risk of data breaches, lateral movement within networks, and potential compromise of sensitive corporate information. The vulnerability's persistence in newer releases also suggests inadequate security testing processes and highlights the need for more robust quality assurance procedures in security software development.
Mitigation strategies for CVE-2011-2678 should prioritize immediate patching of affected Cisco VPN Client versions to address the permission configuration issue. Organizations should implement strict access control policies that ensure system components are not granted unnecessary permissions, following the principle of least privilege as outlined in security best practices. System administrators should conduct thorough audits of file permissions for critical system executables and verify that only authorized users or processes have write access to sensitive files. The implementation of application whitelisting solutions can provide additional protection by preventing unauthorized executable files from running on systems. Network segmentation and monitoring should be enhanced to detect unusual activities that might indicate exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify similar permission misconfigurations across the enterprise environment. Additionally, organizations should consider implementing mandatory access controls and security frameworks that align with NIST cybersecurity guidelines to prevent such regressions from occurring in future software releases. The vulnerability serves as a reminder of the critical importance of maintaining secure default configurations and the necessity of regular security reviews to prevent the reintroduction of known security flaws.