CVE-2026-63767 in ktransformers
Summary
by MITRE • 07/20/2026
ktransformers through 0.6.3, fixed in commit def0f93, contains an unauthenticated pickle deserialization vulnerability that allows remote attackers to execute arbitrary commands by sending crafted pickle payloads to the SchedulerServer ZMQ ROUTER socket bound to all interfaces. Attackers can exploit malicious __reduce__ methods embedded in crafted pickle payloads to execute arbitrary shell commands as the server process.
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Analysis
by VulDB Data Team • 07/20/2026
The ktransformers library through version 0.6.3 contains a critical unauthenticated pickle deserialization vulnerability that represents a significant security risk for systems utilizing the SchedulerServer component. This vulnerability exists within the ZMQ ROUTER socket implementation that binds to all network interfaces, creating an attack surface where remote adversaries can submit maliciously crafted pickle payloads directly to the server. The flaw stems from the library's failure to implement proper authentication mechanisms before processing incoming pickle data, allowing any remote attacker to establish a connection and submit potentially dangerous serialized objects. This issue is particularly concerning because it enables arbitrary code execution with the privileges of the running server process, which could lead to complete system compromise if the service operates with elevated permissions.
The technical exploitation of this vulnerability relies on the inherent dangers of Python's pickle module, which is designed for object serialization and deserialization but lacks proper security controls for untrusted input. When the SchedulerServer processes incoming data through the ZMQ ROUTER socket, it attempts to deserialize any received pickle payload without sufficient validation or authentication checks. Attackers can craft malicious pickle objects containing specially constructed _reduce_ methods that define how objects should be reconstructed during deserialization. These methods can contain arbitrary Python code execution instructions that are triggered when the pickle module processes the serialized data, effectively allowing remote command execution capabilities. The vulnerability is further amplified by the fact that the ZMQ socket binds to all interfaces, meaning the attack surface extends beyond local network boundaries and can be exploited from anywhere on the internet.
The operational impact of this vulnerability is severe and multifaceted, potentially allowing attackers to gain complete control over affected systems running ktransformers versions 0.6.3 or earlier. An attacker who successfully exploits this vulnerability could execute arbitrary shell commands with the privileges of the server process, which might include administrative rights depending on how the service is configured. This could lead to data exfiltration, system modification, privilege escalation to other services, or even lateral movement within a network infrastructure. The remote nature of the attack means that defenders have limited opportunities to detect or prevent exploitation before it occurs, as no authentication or authorization checks are performed prior to deserialization processing. Additionally, since pickle deserialization vulnerabilities often work across different platforms and architectures, the impact extends beyond specific operating system boundaries, making this vulnerability particularly dangerous in diverse computing environments.
The vulnerability aligns with common weakness enumerations such as CWE-502, which specifically addresses "Deserialization of Untrusted Data" as a critical security concern. This weakness category encompasses the fundamental flaw present in ktransformers where untrusted input is processed through deserialization mechanisms without proper validation or sandboxing. From an attacker perspective, this vulnerability maps directly to tactics and techniques described in the ATT&CK framework under T1059 for Command and Scripting Interpreter and T1203 for Exploitation for Client Execution. The attack path follows a typical exploitation pattern where an adversary establishes a remote connection, crafts malicious payloads using known pickle vulnerabilities, and executes commands on the target system with the privileges of the affected service. The fix implemented in commit def0f93 addresses this by implementing proper authentication mechanisms and removing or securing the pickle deserialization functionality within the SchedulerServer component. Organizations should immediately update to versions that include this patch and consider implementing network segmentation, firewall rules, and monitoring for unusual ZMQ traffic patterns as additional defensive measures against similar vulnerabilities.