CVE-2011-4231 in IOS XE
Summary
by MITRE
Cisco IOS 15.1 and 15.2 and IOS XE 3.x, when configured as an IPsec hub with X.509 certificates in use, allows remote authenticated users to cause a denial of service (segmentation fault and device crash) via unspecified vectors, aka Bug ID CSCtq61128.
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Analysis
by VulDB Data Team • 01/29/2018
Cisco IOS versions 15.1 and 15.2, along with IOS XE 3.x, contain a critical vulnerability in their IPsec hub implementation that can be exploited by remotely authenticated attackers to trigger denial of service conditions. This vulnerability specifically affects devices configured with X.509 certificates for IPsec authentication, creating a scenario where legitimate users can cause system crashes through unspecified attack vectors. The flaw manifests as segmentation faults that ultimately lead to complete device crashes, effectively rendering the network infrastructure unavailable to authorized users.
The technical nature of this vulnerability stems from improper handling of X.509 certificates within the IPsec hub configuration framework. When devices operate in hub mode with certificate-based authentication, the processing of certificate validation and negotiation routines contains memory management errors that result in segmentation faults. These faults occur during the normal operation of IPsec tunnels when authenticated users establish connections, suggesting that the vulnerability is not limited to specific attack scenarios but rather emerges from the core certificate processing logic within the IOS IPsec implementation.
The operational impact of this vulnerability is severe as it allows authenticated attackers to disrupt network services without requiring privileged access or specialized tools. Since the attack can be executed by remote authenticated users, it represents a significant threat to network availability, particularly in environments where IPsec hubs serve as critical infrastructure components for secure communications. The segmentation fault condition causes complete device crashes, requiring manual intervention to restore service, which can result in extended downtime and potential business disruption.
This vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and demonstrates how improper certificate handling can lead to memory corruption issues. From an ATT&CK framework perspective, this represents a denial of service attack vector that can be classified under TA0040 (Impact) with techniques such as T1499 (Endpoint Denial of Service) and T1566 (Phishing for Information). The fact that this affects multiple IOS versions including both 15.1/15.2 and 3.x releases indicates a fundamental flaw in the certificate processing code that requires comprehensive patching across affected platforms.
Mitigation strategies should include immediate deployment of Cisco's security patches addressing Bug ID CSCtq61128, which specifically targets this certificate handling vulnerability. Network administrators should also consider implementing additional monitoring for unusual IPsec tunnel behavior and segmentation fault occurrences. The patching process requires careful planning due to the critical nature of the vulnerability, as unpatched systems remain susceptible to complete device crashes that can compromise network availability. Organizations should also review their IPsec hub configurations to minimize exposure and consider alternative authentication methods while awaiting full patch deployment across their network infrastructure.