CVE-2026-102483 in NTPsec
Summary
by MITRE • 10/21/2026
Reachable exit in NTPsec ntpd 1.1.4 through 1.2.5 allows a remote attacker to terminate the daemon via an NTS request with excess NTS Cookie Placeholder extension fields.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified within NTPsec versions ranging from 1.1.4 to 1.2.5 represents a critical availability risk stemming from improper input validation in the Network Time Security implementation of the ntpd daemon. This flaw specifically affects the handling of extension fields found within NTS packets, which are designed to enhance the security and integrity of time synchronization messages over UDP. The core technical deficiency lies in the processing logic for the Cookie Placeholder extension field during the establishment or maintenance of an NTS session. When a remote attacker constructs a maliciously crafted NTS request containing an excessive number of these placeholder fields, the daemon fails to enforce appropriate bounds checking on the total size or count of extensions before proceeding with resource allocation and state management operations.
This lack of validation leads directly to a reachable exit condition within the application logic rather than a traditional buffer overflow that might allow for code execution. The ntpd process interprets the malformed packet as invalid due to the structural anomaly caused by the excess fields, triggering an internal error handling routine that terminates the daemon instance abruptly. While this behavior prevents potential exploitation of more severe vulnerabilities such as remote code execution or arbitrary memory corruption in some contexts, it effectively results in a Denial of Service attack against any host relying on NTPsec for time synchronization. The abrupt termination disrupts all ongoing network time services and requires manual intervention or automated restart mechanisms to restore functionality, thereby compromising the availability guarantee that is central to infrastructure stability.
From an industry standard perspective, this vulnerability aligns with CWE-20 Improper Input Validation, as the software fails to verify that user-supplied input conforms to expected structural constraints before processing it further into critical system resources. Furthermore, in the context of the MITRE ATT&CK framework, this behavior is categorized under T1499 Endpoint Denial of Service, specifically reflecting techniques where an attacker overwhelms or exhausts computational resources or triggers application crashes through malformed inputs rather than brute-force volume attacks alone. The specific vector involves exploiting protocol-level ambiguities in extension field handling to force a state transition that the developer did not anticipate as a valid operational path for normal traffic.
The operational impact of this flaw is significant for environments where high availability and continuous time synchronization are mandatory, such as financial trading platforms, distributed database clusters, or critical infrastructure control systems. An attacker with network access to the NTP server can exploit this condition without authentication if the service is exposed publicly or within a compromised internal segment. The consequence is not data loss or unauthorized access but rather a complete cessation of time services for that node until the daemon is restarted. This disruption can lead to cascading failures in systems dependent on accurate timestamps, including security certificate validation, log correlation, and distributed consensus algorithms like Raft or Paxos which rely heavily on synchronized clocks.
Mitigation strategies should prioritize immediate patching to versions of NTPsec released after 1.2.5 where the input validation logic for extension fields has been hardened. Administrators must ensure that their deployment pipelines include automated updates for time synchronization services, given the critical nature of these daemons in modern IT infrastructure. In scenarios where upgrading is not immediately feasible, network-level controls such as Access Control Lists or firewall rules should be implemented to restrict NTS traffic sources to known and trusted peers only. Additionally, deploying intrusion detection systems capable of identifying anomalous packet structures with excessive extension fields can provide an early warning layer against exploitation attempts while the underlying software vulnerability remains unpatched in legacy environments.