CVE-2015-6280 in IOS
Summary
by MITRE
The SSHv2 functionality in Cisco IOS 15.2, 15.3, 15.4, and 15.5 and IOS XE 3.6E before 3.6.3E, 3.7E before 3.7.1E, 3.10S before 3.10.6S, 3.11S before 3.11.4S, 3.12S before 3.12.3S, 3.13S before 3.13.3S, and 3.14S before 3.14.1S does not properly implement RSA authentication, which allows remote attackers to obtain login access by leveraging knowledge of a username and the associated public key, aka Bug ID CSCus73013.
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Analysis
by VulDB Data Team • 11/18/2024
The vulnerability described in CVE-2015-6280 represents a critical weakness in Cisco IOS and IOS XE implementations of SSHv2 authentication mechanisms. This flaw specifically affects multiple versions of Cisco's network operating systems, creating a significant security risk that impacts enterprise and service provider networks worldwide. The vulnerability stems from improper implementation of RSA authentication within the SSH protocol, which fundamentally undermines the security assurances that SSH connections are designed to provide. Attackers can exploit this weakness to gain unauthorized access to network devices by leveraging knowledge of a valid username and the corresponding public key, effectively bypassing traditional authentication mechanisms that should require private key possession or password verification.
The technical flaw manifests in the SSHv2 RSA authentication implementation where the system fails to properly validate the cryptographic signature process during authentication. This improper handling allows attackers to craft specially crafted authentication requests that can succeed without possessing the legitimate private key. The vulnerability specifically affects the cryptographic verification process where the system should validate that the signature was created using the private key corresponding to the public key presented. However, due to the flawed implementation, the system accepts authentication attempts that should have been rejected, creating a backdoor access path for malicious actors. This weakness operates at the protocol level within the SSH implementation, making it particularly dangerous as it can be exploited from remote locations without requiring physical access to the network devices.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it fundamentally compromises the integrity of network device security. Network administrators who rely on SSH for device management and configuration access face a severe risk of unauthorized device compromise, which could lead to complete network control by attackers. The vulnerability affects critical network infrastructure components including routers, switches, and firewalls that are essential for network operations, potentially enabling attackers to redirect traffic, modify routing tables, or establish persistent backdoors within the network. The attack vector is particularly concerning as it requires minimal information - just a valid username and public key - making it accessible to attackers who may have obtained this information through other means such as network reconnaissance or previous breaches. This vulnerability can be leveraged as part of broader attack campaigns targeting network infrastructure, potentially enabling lateral movement and privilege escalation within compromised networks.
Mitigation strategies for CVE-2015-6280 require immediate action from network administrators to apply the relevant Cisco security patches and updates to affected systems. The vulnerability can be addressed through firmware upgrades to versions that contain the corrected SSHv2 RSA authentication implementation, with Cisco releasing specific patches for each affected software version. Organizations should also implement additional security controls including disabling SSHv2 authentication where possible, implementing stronger authentication mechanisms such as two-factor authentication, and monitoring for unauthorized authentication attempts. Network segmentation and access control measures should be strengthened to limit the potential impact of successful exploitation, while regular security audits should verify that all network devices have been properly updated and that the vulnerability has been fully remediated. The remediation process must be carefully coordinated to avoid service disruption while ensuring complete protection against this specific vulnerability that has been identified in multiple versions of Cisco's operating systems. This vulnerability aligns with CWE-310 and represents a cryptographic weakness that enables authentication bypass, and may be leveraged by attackers following techniques described in the MITRE ATT&CK framework under privilege escalation and credential access tactics.