CVE-2016-1356 in FireSIGHT System Software
Summary
by MITRE
Cisco FireSIGHT System Software 6.1.0 does not use a constant-time algorithm for verifying credentials, which makes it easier for remote attackers to enumerate valid usernames by measuring timing differences, aka Bug ID CSCuy41615.
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Analysis
by VulDB Data Team • 09/01/2018
The vulnerability described in CVE-2016-1356 represents a critical timing attack susceptibility within Cisco FireSIGHT System Software version 6.1.0. This flaw resides in the authentication mechanism where the system fails to implement constant-time algorithms for credential verification, creating a predictable timing pattern that can be exploited by remote attackers. The vulnerability specifically affects the software's handling of user authentication processes, where legitimate credentials take a different amount of time to process compared to invalid ones, thereby exposing the system to systematic username enumeration attacks.
The technical implementation of this vulnerability stems from the absence of constant-time comparison operations during the authentication process. When the system validates user credentials, it performs a sequential comparison that varies in execution time based on whether the input matches the stored hash or not. This timing variation occurs because the system processes each character of the password sequentially and terminates early when a mismatch is detected, allowing attackers to measure the time difference between valid and invalid authentication attempts. The vulnerability directly relates to CWE-204, which categorizes weaknesses involving timing differences in security-critical operations, and aligns with ATT&CK technique T1212 for exploitation of information disclosures through timing attacks.
From an operational perspective, this vulnerability enables attackers to systematically enumerate valid usernames through repeated authentication attempts, measuring response times to distinguish between valid and invalid accounts. The impact extends beyond simple credential theft as it provides attackers with a foundational foothold for further exploitation attempts, potentially leading to unauthorized system access and privilege escalation. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter without requiring physical access or prior authentication, making it particularly dangerous for network security systems that are designed to protect against such threats.
Security professionals should implement multiple mitigation strategies to address this vulnerability effectively. The primary recommendation involves upgrading to Cisco FireSIGHT System Software versions that incorporate constant-time authentication algorithms, which eliminate the timing variations that enable credential enumeration. Additionally, implementing rate limiting and account lockout mechanisms can significantly reduce the effectiveness of automated enumeration attacks by limiting the number of authentication attempts within a given timeframe. Network segmentation and intrusion detection systems should also be configured to monitor for unusual authentication patterns that may indicate timing-based attacks. Organizations should also consider implementing multi-factor authentication to add additional layers of security beyond password-based verification, as this mitigation approach reduces the overall risk even if the timing vulnerability remains unpatched. The vulnerability demonstrates the critical importance of constant-time algorithm implementation in security-critical operations and serves as a reminder that seemingly minor implementation details can have significant security implications in network defense systems.