CVE-2018-16873 in Google
Summary
by MITRE
In Go before 1.10.6 and 1.11.x before 1.11.3, the "go get" command is vulnerable to remote code execution when executed with the -u flag and the import path of a malicious Go package, or a package that imports it directly or indirectly. Specifically, it is only vulnerable in GOPATH mode, but not in module mode (the distinction is documented at https://golang.org/cmd/go/#hdr-Module_aware_go_get). Using custom domains, it's possible to arrange things so that a Git repository is cloned to a folder named ".git" by using a vanity import path that ends with "/.git". If the Git repository root contains a "HEAD" file, a "config" file, an "objects" directory, a "refs" directory, with some work to ensure the proper ordering of operations, "go get -u" can be tricked into considering the parent directory as a repository root, and running Git commands on it. That will use the "config" file in the original Git repository root for its configuration, and if that config file contains malicious commands, they will execute on the system running "go get -u".
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability described in CVE-2018-16873 represents a critical remote code execution flaw in the go get command of the Go programming language ecosystem. This vulnerability specifically affects Go versions prior to 1.10.6 and 1.11.3, creating a dangerous attack surface when developers execute the go get command with the -u flag in GOPATH mode. The flaw exploits the way Go handles package imports and Git repository cloning operations, particularly when dealing with vanity import paths that manipulate the filesystem structure to execute malicious commands. The vulnerability operates through a sophisticated manipulation of Git repository metadata and directory structures that can be leveraged by attackers to gain arbitrary code execution privileges on systems running vulnerable versions of Go.
The technical mechanism of this vulnerability stems from how Go's package management system processes Git repositories during the go get -u operation. When a malicious package is imported, the system can be tricked into cloning a Git repository to a directory named ".git" through carefully crafted vanity import paths. This manipulation allows attackers to place malicious configuration files within the repository structure, specifically targeting the config file that Git uses for its operations. The vulnerability exploits the fact that Go's implementation does not properly validate the repository structure when processing updates, leading to situations where Git commands executed during the update process operate on unintended parent directories. This creates a scenario where the Git configuration file from the malicious repository can contain commands that are executed with the privileges of the user running the go get -u command.
The operational impact of this vulnerability is severe and far-reaching within development environments that utilize the Go programming language. Any developer who executes go get -u on a system running vulnerable Go versions is at risk of having their system compromised through seemingly legitimate package updates. The vulnerability is particularly dangerous because it can be exploited through standard package management workflows without requiring special privileges or complex attack vectors. Attackers can craft malicious vanity import paths that appear legitimate to developers while simultaneously setting up malicious Git repository structures that execute code upon package update operations. This makes the vulnerability particularly insidious as it can be exploited during routine development activities, potentially affecting entire development teams or organizations that rely on Go package management.
The vulnerability aligns with CWE-434, which addresses the insecure handling of file uploads or downloads, and demonstrates how improper validation of repository structures can lead to arbitrary code execution. From an ATT&CK perspective, this vulnerability maps to T1059.001 (Command and Scripting Interpreter: PowerShell) and T1059.007 (Command and Scripting Interpreter: JavaScript) through the execution of malicious commands within Git configuration files. The attack chain typically involves an attacker creating a malicious Go package with a vanity import path that, when processed by go get -u, triggers the Git repository manipulation and subsequent command execution. Organizations should implement immediate mitigations including updating to patched Go versions, implementing network controls to restrict access to malicious repositories, and establishing code review processes that prevent the execution of untrusted package updates in production environments.
The root cause of this vulnerability lies in the insufficient validation of Git repository structures during package update operations within GOPATH mode. Go's package management system failed to properly verify that repository metadata files are not being manipulated to execute code outside of intended boundaries. The vulnerability demonstrates how the interaction between package management systems and version control systems can create unexpected security implications when proper boundary checks are not implemented. This flaw highlights the importance of considering the broader ecosystem implications when designing package management systems and underscores the need for comprehensive input validation and privilege separation in development tools. Organizations should also consider implementing security awareness training for developers to recognize potentially malicious package imports and to understand the risks associated with executing package update commands on untrusted repositories.