CVE-2021-39160 in nbgitpuller
Summary
by MITRE • 08/25/2021
nbgitpuller is a Jupyter server extension to sync a git repository one-way to a local path. Due to unsanitized input, visiting maliciously crafted links could result in arbitrary code execution in the user environment. This has been resolved in version 0.10.2 and all users are advised to upgrade. No work around exist for users who can not upgrade.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 08/29/2021
The nbgitpuller Jupyter server extension represents a critical security vulnerability identified as CVE-2021-39160, which exposes users to arbitrary code execution risks through unsanitized input handling. This vulnerability specifically affects the one-way synchronization functionality between git repositories and local paths within Jupyter environments, creating a dangerous attack surface where maliciously crafted links can compromise user systems. The flaw exists in how the extension processes user-provided input parameters, particularly those related to git repository URLs and path specifications, without proper validation or sanitization mechanisms.
The technical implementation of this vulnerability stems from insufficient input validation within the nbgitpuller extension's handling of git repository synchronization commands. When users visit maliciously crafted links, the extension processes these inputs directly without adequate sanitization, allowing attackers to inject arbitrary commands that execute within the user's local environment. This type of vulnerability maps directly to CWE-20, which describes improper input validation, and represents a classic command injection vulnerability that can escalate to full system compromise. The attack vector leverages the trust relationship between the Jupyter server and the user's local environment, exploiting the extension's assumption that all input parameters are legitimate and safe for execution.
The operational impact of CVE-2021-39160 extends beyond simple code execution to encompass complete system compromise within Jupyter notebook environments, particularly in research institutions, data science teams, and educational settings where these extensions are commonly deployed. Attackers can leverage this vulnerability to execute malicious code with the privileges of the affected user, potentially accessing sensitive data, establishing persistent backdoors, or using the compromised system as a launch point for further attacks within the network. The vulnerability affects all versions prior to 0.10.2, leaving users who cannot immediately upgrade in a particularly dangerous position where no viable workaround exists to mitigate the risk. This makes the vulnerability especially concerning in environments where upgrading software components is a complex or time-consuming process.
Security mitigations for CVE-2021-39160 primarily focus on immediate software upgrading to version 0.10.2 or later, which incorporates proper input sanitization and validation mechanisms. Organizations should implement comprehensive vulnerability management procedures to ensure timely patch deployment across all Jupyter environments and server extensions. The remediation aligns with ATT&CK technique T1059.001 for command and scripting interpreter execution, as the vulnerability enables attackers to execute arbitrary commands through the compromised extension. Additionally, administrators should consider implementing network-level restrictions and monitoring for suspicious git repository access patterns, while also establishing secure coding practices for server extensions that emphasize input validation and proper parameter sanitization to prevent similar vulnerabilities in future deployments.