CVE-2016-1335 in StarOS
Summary
by MITRE
The SSH implementation in Cisco StarOS before 19.3.M0.62771 and 20.x before 20.0.M0.62768 on ASR 5000 devices mishandles a multi-user public-key authentication configuration, which allows remote authenticated users to gain privileges by establishing a connection from an endpoint that was previously used for an administrator's connection, aka Bug ID CSCux22492.
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Analysis
by VulDB Data Team • 07/08/2022
The vulnerability described in CVE-2016-1335 represents a critical privilege escalation flaw within Cisco StarOS operating system versions prior to specific patch levels. This issue affects Cisco ASR 5000 series devices and stems from improper handling of public-key authentication in multi-user environments. The flaw specifically manifests when multiple users share the same endpoint or connection path, creating a scenario where authentication state can be improperly reused or manipulated. The vulnerability is particularly concerning as it allows authenticated remote attackers to escalate their privileges without requiring additional credentials or complex attack vectors.
The technical root cause of this vulnerability lies in the improper session management and authentication state handling within the SSH implementation of Cisco StarOS. When an administrator establishes a connection from a particular endpoint, the system fails to properly invalidate or reset authentication contexts when subsequent users attempt to establish connections from the same endpoint. This creates a scenario where the system may incorrectly associate the new user's authentication attempt with the previous administrator session, allowing unauthorized privilege escalation. The flaw operates at the application layer of the network stack and specifically targets the Secure Shell protocol implementation that Cisco uses for remote device management.
From an operational impact perspective, this vulnerability presents a significant risk to network infrastructure security as it enables attackers to potentially gain administrative access to critical network equipment. The attack requires only remote authenticated access, meaning that an attacker who has already established a legitimate user session can exploit this flaw to elevate their privileges to administrator level. This creates a dangerous scenario where compromised user accounts can be leveraged to gain full control over network devices, potentially leading to complete network compromise, data exfiltration, or service disruption. The vulnerability directly impacts the principle of least privilege and undermines the security model of the affected Cisco devices.
Mitigation strategies for CVE-2016-1335 should focus on immediate patch deployment to the affected Cisco StarOS versions, specifically upgrading to versions 19.3.M0.62771 or later, or 20.0.M0.62768 or later on ASR 5000 devices. Organizations should also implement network segmentation and access controls to limit the attack surface, ensuring that only authorized personnel can establish initial connections to these devices. Network monitoring should be enhanced to detect unusual authentication patterns or privilege escalation attempts. Additionally, administrators should regularly review and audit SSH access logs to identify potential exploitation attempts. This vulnerability aligns with CWE-284 which addresses improper access control, and maps to ATT&CK technique T1078 for valid accounts and privilege escalation, highlighting the importance of proper session management and authentication state handling in network security implementations.