CVE-2026-12171 in auto-changelog
Summary
by MITRE • 10/05/2026
auto-changelog before 2.6.1 merges configuration from inside the target repository (the .auto-changelog file and the auto-changelog key in package.json) into its options, and honors security-sensitive options from that untrusted source. The handlebarsSetup option is passed to require(), so running auto-changelog over attacker-controlled repository content (for example, in a CI workflow that checks out an untrusted pull request head, or locally on a forked or third-party repository) executes attacker-chosen code with the privileges of the invoking user or CI job, including access to workflow secrets, without the repository dependencies ever being installed. The plugins option similarly loads attacker-controlled modules from the repository. Under the same conditions, appendGitLog/appendGitTag allow git argument injection (e.g. --output= to write arbitrary files), output allows writing attacker-influenced content to arbitrary paths, and template causes an outbound request to an attacker-chosen URL. Version 2.6.1 treats in-repository configuration as untrusted and refuses to run when it sets these options, unless the new --unsafe-config flag is passed.
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Analysis
by VulDB Data Team • 10/05/2026
The vulnerability identified in auto-changelog versions prior to 2.6.1 represents a critical security flaw rooted in insecure handling of external configuration sources within automated software development workflows. The core issue arises from the tool's design philosophy, which prioritizes convenience by automatically merging configuration settings found directly inside the target repository into its operational options. This behavior includes reading the .auto-changelog file and specific keys within package.json without sufficient validation or isolation mechanisms. By treating these in-repository configurations as trusted defaults rather than untrusted input, the application creates a significant attack surface for malicious actors who can manipulate repository contents to execute arbitrary actions on behalf of the user running the tool. This flaw is particularly dangerous because it bypasses traditional dependency installation checks; since the configuration files are parsed directly from the file system before any npm install or yarn command executes, an attacker does not need to compromise the project's dependencies to achieve code execution.
The most severe aspect of this vulnerability involves the handlebarsSetup option, which accepts a string that is subsequently passed to Node.js require() function. This mechanism allows for arbitrary JavaScript code execution with the privileges of the user or CI job invoking auto-changelog. In continuous integration environments where tools are frequently run against untrusted pull request heads or forked repositories, an attacker can craft a malicious .auto-changelog file containing a handlebarsSetup value that points to a remote module or executes inline code. Upon running the tool, this configuration triggers immediate execution of the attacker's payload. The impact is severe because CI environments often possess elevated privileges and access to sensitive workflow secrets such as API keys, deployment tokens, and cloud credentials. Consequently, an attacker can exfiltrate these secrets or compromise the build infrastructure without ever needing to install malicious packages in the target repository, effectively bypassing dependency scanning tools that rely on lockfiles for threat detection.
Beyond code execution via handlebarsSetup, other configuration options present distinct but equally dangerous risks when manipulated through untrusted input. The plugins option allows the loading of attacker-controlled modules from the repository, further expanding the attack vector for arbitrary code execution and potential supply chain contamination. Additionally, the appendGitLog and appendGitTag functions are susceptible to git argument injection attacks. By manipulating these options, an adversary can inject command-line arguments such as --output= followed by a path to write arbitrary files onto the host system. This capability enables file overwrites that could disrupt build processes or plant malicious artifacts into critical directories. Furthermore, the output option permits writing attacker-influenced content to arbitrary paths on the filesystem, while the template option facilitates outbound network requests to URLs chosen entirely by the attacker. These features collectively allow for data exfiltration via DNS or HTTP channels and local file system manipulation, compromising both confidentiality and integrity of the development environment.
From a classification perspective, this vulnerability aligns with CWE-94 Improper Control of Generation of Code (Code Injection) due to the execution of arbitrary code through require() calls derived from untrusted input. It also relates closely to CWE-502 Deserialization of Untrusted Data and CWE-78 OS Command Injection for the git argument injection aspects. In terms of adversary tactics, this flaw maps directly to MITRE ATT&CK technique T1059 Command and Scripting Interpreter, specifically allowing attackers to execute commands within a CI/CD pipeline context. The attack pattern is consistent with supply chain attacks where trust boundaries are blurred between project configuration files and application logic, exploiting the assumption that repository contents are safe for automated processing tools.
Mitigation strategies must focus on strict input validation and secure defaults rather than relying on user-provided configurations from untrusted sources. For users of auto-changelog versions prior to 2.6.1, immediate remediation involves upgrading to version 2.6.1 or later, which explicitly treats in-repository configuration as untrusted by default. This updated version refuses to run if sensitive options are set within the repository unless an explicit --unsafe-config flag is passed, thereby forcing a deliberate and conscious decision to trust external input. In CI/CD pipelines, it is crucial to audit workflows that checkout third-party code or pull request heads before running any tooling that parses configuration files from those sources. Implementing strict allowlists for allowed options and disabling dynamic loading features by default can further reduce risk. Security teams should also consider implementing static analysis rules in their linters to detect potential injection points in build scripts and ensure that no sensitive data is exposed through logs or output files generated during the changelog creation process.