CVE-2011-4667 in IOS
Summary
by MITRE
The encryption library in Cisco IOS Software 15.2(1)T, 15.2(1)T1, and 15.2(2)T, Cisco NX-OS in Cisco MDS 9222i Multiservice Modular Switch, Cisco MDS 9000 18/4-Port Multiservice Module, and Cisco MDS 9000 Storage Services Node module before 5.2(6), and Cisco IOS in Cisco VPN Services Port Adaptor for Catalyst 6500 12.2(33)SXI, and 12.2(33)SXJ when IP Security (aka IPSec) is used, allows remote attackers to obtain unencrypted packets from encrypted sessions.
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Analysis
by VulDB Data Team • 11/19/2019
The vulnerability described in CVE-2011-4667 represents a critical weakness in the encryption implementation of Cisco's networking software platforms, specifically affecting IOS and NX-OS operating systems. This flaw manifests within the IP Security (IPSec) framework where the encryption library fails to properly maintain the confidentiality of network traffic, creating a scenario where encrypted sessions can be compromised to reveal unencrypted data. The affected versions span multiple Cisco product lines including enterprise routers, storage switches, and VPN services adaptors, indicating a widespread impact across the vendor's networking portfolio. The vulnerability specifically targets the cryptographic processing within IPSec implementations, where the encryption mechanism becomes vulnerable to exploitation by remote attackers who can manipulate the network traffic flow to extract plaintext data from what should be encrypted communications.
The technical root cause of this vulnerability lies in improper handling of cryptographic operations within the IPSec processing pipeline of Cisco's networking software. When IPSec is enabled on affected devices, the encryption library fails to maintain proper separation between encrypted and unencrypted packet processing, allowing attackers to exploit timing or state-based vulnerabilities in the cryptographic engine. This flaw enables what is known as a "plaintext recovery" attack where the attacker can observe and reconstruct unencrypted portions of the network traffic that flows through affected devices. The vulnerability specifically affects the implementation of IPSec protocols within Cisco's software stack, where the cryptographic processing routines do not properly validate or maintain the integrity of encrypted session states. This represents a direct violation of the confidentiality principles that IPSec is designed to provide, essentially creating a backdoor through which network traffic can be decrypted without proper authorization. The issue falls under the CWE category of cryptographic weakness, specifically related to improper implementation of encryption algorithms and key management processes.
The operational impact of this vulnerability is severe and far-reaching across enterprise and service provider networks that rely on Cisco's networking equipment for secure communications. Remote attackers who can exploit this vulnerability can potentially intercept sensitive data flowing through encrypted IPSec tunnels, including authentication credentials, business data, and other confidential information. This creates a significant risk for organizations that depend on IPSec for securing network communications between branch offices, remote workers, and critical infrastructure components. The vulnerability affects both enterprise routing platforms and storage switching environments, meaning that the compromise could extend from network perimeter security to internal storage network communications. Organizations using affected Cisco VPN Services Port Adaptors are particularly vulnerable as these devices often serve as critical gateways for remote access and site-to-site connections, making them prime targets for attackers seeking to gain unauthorized access to network resources. The remote nature of the attack means that adversaries do not require physical access to the network infrastructure, making the vulnerability particularly dangerous in environments where network security is paramount.
Mitigation strategies for this vulnerability require immediate attention from network administrators and security teams responsible for Cisco networking infrastructure. The primary recommended approach is to upgrade all affected Cisco devices to patched versions of IOS and NX-OS software that contain corrected implementations of the IPSec cryptographic processing. Cisco released security advisories and patches specifically addressing this vulnerability, and organizations should prioritize applying these updates to all affected devices across their network infrastructure. Network segmentation and monitoring should be enhanced to detect anomalous traffic patterns that might indicate exploitation attempts, particularly focusing on IPSec traffic flows and potential plaintext recovery attempts. Organizations should also consider implementing additional security controls such as network access controls and traffic filtering to limit the potential impact if exploitation occurs. The vulnerability's impact on both enterprise and storage networking environments means that security teams must coordinate across different network domains to ensure comprehensive protection. Given the nature of the vulnerability and its potential for data exfiltration, organizations should also conduct thorough security assessments of their network communications and implement additional monitoring for unauthorized access attempts. The remediation process should include not only software updates but also network configuration reviews to ensure that IPSec implementations are properly configured to avoid similar vulnerabilities in other components of the network infrastructure.