CVE-2016-1567 in chrony
Summary
by MITRE
chrony before 1.31.2 and 2.x before 2.2.1 do not verify peer associations of symmetric keys when authenticating packets, which might allow remote attackers to conduct impersonation attacks via an arbitrary trusted key, aka a "skeleton key."
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Analysis
by VulDB Data Team • 10/14/2024
The vulnerability described in CVE-2016-1567 affects the chrony time synchronization daemon version 1.31.1 and earlier, as well as version 2.2.0 and earlier in the 2.x series. This flaw represents a critical weakness in the authentication mechanism of the NTP (Network Time Protocol) implementation that chrony uses for time synchronization. The vulnerability stems from insufficient validation of peer associations when processing symmetric key authentication, creating a scenario where malicious actors can exploit the system through what is known as a "skeleton key" attack vector.
The technical flaw lies in the authentication process where chrony fails to properly verify that peer associations match expected symmetric key associations during packet authentication. This allows remote attackers to bypass authentication mechanisms by presenting an arbitrary trusted key, effectively enabling them to impersonate legitimate time servers or clients within the network. The vulnerability specifically impacts the cryptographic authentication procedures that should ensure only authorized peers can participate in time synchronization operations. This weakness is categorized under CWE-310 as Cryptographic Issues, more specifically related to improper authentication of symmetric keys and insufficient verification of peer associations.
The operational impact of this vulnerability is significant as it allows remote attackers to conduct impersonation attacks that can compromise the integrity of time synchronization within affected networks. When exploited, this vulnerability can lead to time drift issues, potential denial of service conditions, and more serious security implications such as man-in-the-middle attacks on time-critical systems. The attack can be particularly damaging in environments where precise time synchronization is critical for security operations, such as financial transactions, logging systems, or network security infrastructure. The ability to use an arbitrary trusted key means that attackers do not need to possess specific cryptographic keys, making the attack surface much broader and more accessible than traditional key-based authentication bypasses.
Organizations affected by this vulnerability should immediately implement mitigations including upgrading to chrony versions 1.31.2 or 2.2.1 and later, which contain the necessary patches to properly validate peer associations during symmetric key authentication. Network administrators should also consider implementing additional monitoring for unusual time synchronization behavior and peer associations that might indicate exploitation attempts. The mitigation strategy aligns with ATT&CK technique T1562.001 which involves disabling or modifying system security tools, though in this case the issue is more about proper implementation of security controls rather than disabling them. Additionally, organizations should review their network segmentation and access controls to limit exposure of time synchronization services to only trusted networks and hosts, reducing the potential impact of successful exploitation attempts.