Summary
Terragrunt: Arbitrary File Deletion via Malicious Module Manifest
Terragrunt is vulnerable to an arbitrary file deletion flaw when downloading external modules. If a remote module contains a maliciously crafted .terragrunt-module-manifest file, Terragrunt can be tricked into deleting files anywhere on the local filesystem that the Terragrunt process has access to.
Affected Versions
- Terragrunt <
v1.0.4
Workarounds
If users cannot upgrade immediately, they can mitigate this risk by:
- Strictly auditing the source URLs of all remote modules used in their Terragrunt configurations.
- Only consuming modules from trusted, internally vetted sources or verified registries.
- Pinning module versions to specific, known-safe Git commit SHAs rather than mutable tags or branches.
Technical Details
Terragrunt tracks files copied into a downloaded module's working directory using a .terragrunt-module-manifest file. During the directory cleanup process, Terragrunt decodes the entries in this manifest and removes the listed files to prepare a fresh directory for OpenTofu/Terraform runs.
Previously, Terragrunt trusted the manifest provided by the downloaded module without verifying that the paths scheduled for deletion remained within the boundaries of the module's destination directory. An attacker could forge a manifest containing directory traversal paths, causing the cleanup function to target files outside the cache. The patch introduces a secure boundary check to ensure all cleaned paths remain safely isolated inside the intended manifest folder.
Credit
Terragrunt would like to thank Francesco Sabiu (@fsabiu) for discovering and responsibly disclosing this vulnerability.
Impact
This vulnerability impacts users who download and run untrusted or compromised OpenTofu/Terraform modules. The file deletion occurs during the module download and initialization phase, meaning it happens before OpenTofu or Terraform executes.
In a CI/CD environment or automated runner, an attacker-controlled module could delete arbitrary files, causing denial of service in the deployment pipeline. In a local environment, it could lead to the loss of local source code or configuration files.
This vulnerability is a deletion-only primitive; it does not directly allow for arbitrary code execution (RCE) or data exfiltration.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
This vulnerability has been resolved in Terragrunt version v1.0.4.
All users are strongly advised to upgrade.
Frequently Asked Questions
- What is CVE-2026-45099? CVE-2026-45099 is a medium-severity improper input validation vulnerability in github.com/gruntwork-io/terragrunt (go), affecting versions < 1.0.4. It is fixed in 1.0.4. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- Which versions of github.com/gruntwork-io/terragrunt are affected by CVE-2026-45099? github.com/gruntwork-io/terragrunt (go) versions < 1.0.4 is affected.
- Is there a fix for CVE-2026-45099? Yes. CVE-2026-45099 is fixed in 1.0.4. Upgrade to this version or later.
- Is CVE-2026-45099 exploitable, and should I be worried? Whether CVE-2026-45099 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-45099 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-45099? Upgrade
github.com/gruntwork-io/terragruntto 1.0.4 or later.